diff --git a/datadog-integration/data.tf b/datadog-integration/data.tf
index a2104ab..e2d414f 100644
--- a/datadog-integration/data.tf
+++ b/datadog-integration/data.tf
@@ -38,3 +38,4 @@ data "oci_identity_domains_groups" "existing_group_in_domain" {
 data "oci_identity_domain" "domain" {
   domain_id = local.matching_domain_id
 }
+
diff --git a/datadog-integration/delete_stack.sh b/datadog-integration/delete_stack.sh
index 7c8bca2..3841b5e 100755
--- a/datadog-integration/delete_stack.sh
+++ b/datadog-integration/delete_stack.sh
@@ -6,6 +6,7 @@ export OCI_CLI_SUPPRESS_FILE_PERMISSIONS_WARNING=True
 COMPARTMENT=$1
 REGION=$2
 DISPLAY_NAME=$3
+DEFINED_TAGS_JSON="${4:-}"
 
 STACK_IDS=($(oci --region "$REGION" resource-manager stack list --compartment-id $COMPARTMENT --display-name $DISPLAY_NAME --raw-output | jq -r '.data[]."id"'))
 
@@ -14,12 +15,17 @@ if [[ -z "$STACK_IDS" ]]; then
   exit 0
 fi
 
+DEFINED_TAGS_ARG=()
+if [[ -n "$DEFINED_TAGS_JSON" ]]; then
+  DEFINED_TAGS_ARG=(--defined-tags "$DEFINED_TAGS_JSON")
+fi
+
 echo "Found... stack... Ids: ${STACK_IDS[@]}"
 for STACK_ID in "${STACK_IDS[@]}"; do
   echo "Running...destroy...job...for...stack...: $STACK_ID"
 
   JOB_ID=$(oci --region "$REGION" resource-manager job create-destroy-job \
-    --stack-id "$STACK_ID" --wait-for-state SUCCEEDED --wait-for-state FAILED \
+    --stack-id "$STACK_ID" "${DEFINED_TAGS_ARG[@]}" --wait-for-state SUCCEEDED --wait-for-state FAILED \
     --execution-plan-strategy AUTO_APPROVED \
     --query "data.id" --raw-output)
   
diff --git a/datadog-integration/locals.tf b/datadog-integration/locals.tf
index 4d3c624..8c5a535 100644
--- a/datadog-integration/locals.tf
+++ b/datadog-integration/locals.tf
@@ -3,6 +3,28 @@ locals {
     ownedby = "datadog"
   }
 
+  # Defined tags: parsed from user input (multiline namespace.key:value per line)
+  defined_tags_raw = [
+    for line in split("\n", var.defined_tags != null ? var.defined_tags : "") :
+    trimspace(line) if trimspace(line) != ""
+  ]
+  defined_tags = {
+    for line in local.defined_tags_raw :
+    # Format: namespace.key:value (split on first : so value can contain colons)
+    (split(":", line)[0]) => (
+      length(split(":", line)) > 1 ? join(":", slice(split(":", line), 1, length(split(":", line)))) : ""
+    )
+  }
+
+  # Nested format for stack create --defined-tags (tags the Stack resource in the compartment)
+  compartment_defined_tags = length(local.defined_tags) > 0 ? {
+    for ns in distinct([for k in keys(local.defined_tags) : split(".", k)[0]]) :
+    ns => { for k, v in local.defined_tags : join(".", slice(split(".", k), 1, length(split(".", k)))) => v if split(".", k)[0] == ns }
+  } : {}
+
+  # Prebuilt --defined-tags flag for oci resource-manager stack create (avoids heredoc quoting issues)
+  stack_create_defined_tags_flag = length(keys(local.compartment_defined_tags)) > 0 ? join("", ["--defined-tags '", jsonencode(local.compartment_defined_tags), "'"]) : ""
+
   home_region_name = [
     for region in data.oci_identity_region_subscriptions.subscribed_regions.region_subscriptions : region.region_name
     if region.is_home_region
diff --git a/datadog-integration/main.tf b/datadog-integration/main.tf
index a7d4dba..5b56dcb 100644
--- a/datadog-integration/main.tf
+++ b/datadog-integration/main.tf
@@ -201,6 +201,7 @@ module "compartment" {
   new_compartment_name  = local.new_compartment_name
   parent_compartment_id = var.tenancy_ocid
   tags                  = local.tags
+  defined_tags          = local.defined_tags
 }
 
 module "kms" {
@@ -210,6 +211,7 @@ module "kms" {
   compartment_id  = module.compartment.id
   datadog_api_key = var.datadog_api_key
   tags            = local.tags
+  defined_tags    = local.defined_tags
 }
 
 module "auth" {
@@ -230,6 +232,7 @@ module "auth" {
   dg_sch_name       = local.dg_sch_name
   dg_fn_name        = local.dg_fn_name
   dg_policy_name    = local.dg_policy_name
+  defined_tags      = local.defined_tags
 }
 
 module "key" {
@@ -260,7 +263,8 @@ module "integration" {
   user_ocid                       = module.auth[0].user_id
   subscribed_regions              = tolist(local.final_regions_for_stacks)
   datadog_resource_compartment_id = module.compartment.id
-  logs_enabled                     = var.logs_enabled
+  logs_enabled                    = var.logs_enabled
+  defined_tags                    = local.defined_tags
 }
 
 
diff --git a/datadog-integration/modules/auth/main.tf b/datadog-integration/modules/auth/main.tf
index 566db5e..1306437 100644
--- a/datadog-integration/modules/auth/main.tf
+++ b/datadog-integration/modules/auth/main.tf
@@ -137,6 +137,14 @@ resource "oci_identity_domains_user" "dd_auth" {
         value = freeform_tags.value
       }
     }
+    dynamic "defined_tags" {
+      for_each = var.defined_tags
+      content {
+        namespace = split(".", defined_tags.key)[0]
+        key       = join(".", slice(split(".", defined_tags.key), 1, length(split(".", defined_tags.key))))
+        value     = defined_tags.value
+      }
+    }
   }
 }
 
@@ -161,6 +169,14 @@ resource "oci_identity_domains_group" "dd_auth" {
         value = freeform_tags.value
       }
     }
+    dynamic "defined_tags" {
+      for_each = var.defined_tags
+      content {
+        namespace = split(".", defined_tags.key)[0]
+        key       = join(".", slice(split(".", defined_tags.key), 1, length(split(".", defined_tags.key))))
+        value     = defined_tags.value
+      }
+    }
   }
 }
 
@@ -172,11 +188,13 @@ resource "oci_identity_policy" "dd_auth" {
   statements = [
     "Define tenancy usage-report as ocid1.tenancy.oc1..aaaaaaaaned4fkpkisbwjlr56u7cj63lf3wffbilvqknstgtvzub7vhqkggq",
     "Allow group id ${var.existing_group_id != null && var.existing_group_id != "" ? var.existing_group_id : oci_identity_domains_group.dd_auth[0].ocid} to read all-resources in tenancy",
+    "Allow group id ${var.existing_group_id != null && var.existing_group_id != "" ? var.existing_group_id : oci_identity_domains_group.dd_auth[0].ocid} to use tag-namespaces in tenancy",
     "Allow group id ${var.existing_group_id != null && var.existing_group_id != "" ? var.existing_group_id : oci_identity_domains_group.dd_auth[0].ocid} to manage serviceconnectors in compartment id ${var.compartment_id}",
     "Allow group id ${var.existing_group_id != null && var.existing_group_id != "" ? var.existing_group_id : oci_identity_domains_group.dd_auth[0].ocid} to manage functions-family in compartment id ${var.compartment_id} where ANY {request.permission = 'FN_FUNCTION_UPDATE', request.permission = 'FN_FUNCTION_LIST', request.permission = 'FN_APP_LIST'}",
     "Endorse group id ${var.existing_group_id != null && var.existing_group_id != "" ? var.existing_group_id : oci_identity_domains_group.dd_auth[0].ocid} to read objects in tenancy usage-report"
   ]
   freeform_tags = var.tags
+  defined_tags  = var.defined_tags
 }
 
 resource "oci_identity_domains_dynamic_resource_group" "service_connector" {
@@ -210,4 +228,5 @@ resource "oci_identity_policy" "dynamic_group" {
     "Allow dynamic-group id ${oci_identity_domains_dynamic_resource_group.forwarding_function.ocid} to read secret-bundles in compartment id ${var.compartment_id}"
   ]
   freeform_tags = var.tags
+  defined_tags  = var.defined_tags
 }
diff --git a/datadog-integration/modules/auth/variables.tf b/datadog-integration/modules/auth/variables.tf
index 675ef02..c64a131 100644
--- a/datadog-integration/modules/auth/variables.tf
+++ b/datadog-integration/modules/auth/variables.tf
@@ -11,7 +11,13 @@ variable "user_email" {
 }
 
 variable "tags" {
-  description = "A map of tags to assign to the resource"
+  description = "A map of freeform tags to assign to the resource"
+  type        = map(string)
+  default     = {}
+}
+
+variable "defined_tags" {
+  description = "A map of defined tags to assign to the resource"
   type        = map(string)
   default     = {}
 }
diff --git a/datadog-integration/modules/compartment/main.tf b/datadog-integration/modules/compartment/main.tf
index 892701f..f7af030 100644
--- a/datadog-integration/modules/compartment/main.tf
+++ b/datadog-integration/modules/compartment/main.tf
@@ -20,5 +20,6 @@ resource "oci_identity_compartment" "new" {
   name           = var.new_compartment_name
   description    = "Compartment for Datadog generated resources"
   compartment_id = var.parent_compartment_id
-  freeform_tags  = var.tags
+  freeform_tags = var.tags
+  defined_tags  = var.defined_tags
 }
diff --git a/datadog-integration/modules/compartment/variables.tf b/datadog-integration/modules/compartment/variables.tf
index 59978f2..d5fc1f7 100644
--- a/datadog-integration/modules/compartment/variables.tf
+++ b/datadog-integration/modules/compartment/variables.tf
@@ -10,7 +10,13 @@ variable "parent_compartment_id" {
 }
 
 variable "tags" {
-  description = "A map of tags to assign to the compartment"
+  description = "A map of freeform tags to assign to the compartment"
+  type        = map(string)
+  default     = {}
+}
+
+variable "defined_tags" {
+  description = "A map of defined tags to assign to the compartment"
   type        = map(string)
   default     = {}
 }
diff --git a/datadog-integration/modules/integration/locals.tf b/datadog-integration/modules/integration/locals.tf
index 21c24e2..2bf7b2d 100644
--- a/datadog-integration/modules/integration/locals.tf
+++ b/datadog-integration/modules/integration/locals.tf
@@ -18,8 +18,9 @@ locals {
         dd_compartment_id : var.datadog_resource_compartment_id
         dd_stack_id : try(data.external.stack_info.result.stack_id, "")
         logs_config : {
-          Enabled: var.logs_enabled
+          Enabled : var.logs_enabled
         }
+        defined_tags : [for k, v in var.defined_tags : "${k}:${v}"]
       }
     }
   }
diff --git a/datadog-integration/modules/integration/variables.tf b/datadog-integration/modules/integration/variables.tf
index 695eb7e..b3a2c1e 100644
--- a/datadog-integration/modules/integration/variables.tf
+++ b/datadog-integration/modules/integration/variables.tf
@@ -54,3 +54,9 @@ variable "logs_enabled" {
   description = "Indicates if logs should be enabled/disabled"
   default     = false
 }
+
+variable "defined_tags" {
+  type        = map(string)
+  description = "OCI defined tags applied to resources (namespace.key -> value). Sent to Datadog for integration config."
+  default     = {}
+}
diff --git a/datadog-integration/modules/kms/main.tf b/datadog-integration/modules/kms/main.tf
index 56a8aff..b3cb3a7 100644
--- a/datadog-integration/modules/kms/main.tf
+++ b/datadog-integration/modules/kms/main.tf
@@ -14,6 +14,7 @@ resource "oci_kms_vault" "datadog_vault" {
   display_name   = "datadog-vault"
   vault_type     = "DEFAULT"
   freeform_tags  = var.tags
+  defined_tags   = var.defined_tags
 }
 
 resource "oci_kms_key" "datadog_key" {
@@ -25,6 +26,7 @@ resource "oci_kms_key" "datadog_key" {
   }
   management_endpoint = oci_kms_vault.datadog_vault.management_endpoint
   freeform_tags       = var.tags
+  defined_tags        = var.defined_tags
 }
 
 resource "oci_vault_secret" "api_key" {
@@ -37,5 +39,6 @@ resource "oci_vault_secret" "api_key" {
     content      = base64encode(var.datadog_api_key)
   }
   freeform_tags = var.tags
+  defined_tags  = var.defined_tags
 }
 
diff --git a/datadog-integration/modules/kms/variables.tf b/datadog-integration/modules/kms/variables.tf
index 5a91bbb..878fa09 100644
--- a/datadog-integration/modules/kms/variables.tf
+++ b/datadog-integration/modules/kms/variables.tf
@@ -5,7 +5,13 @@ variable "compartment_id" {
 
 variable "tags" {
   type        = map(string)
-  description = "A map of tags to assign to resources"
+  description = "A map of freeform tags to assign to resources"
+  default     = {}
+}
+
+variable "defined_tags" {
+  type        = map(string)
+  description = "A map of defined tags to assign to resources"
   default     = {}
 }
 
diff --git a/datadog-integration/modules/regional-stacks/locals.tf b/datadog-integration/modules/regional-stacks/locals.tf
index 3856f40..530c8f1 100644
--- a/datadog-integration/modules/regional-stacks/locals.tf
+++ b/datadog-integration/modules/regional-stacks/locals.tf
@@ -1,4 +1,5 @@
 locals {
+  defined_tags_map   = jsondecode(var.defined_tags)
   registry_host      = lower("${var.region_key}.ocir.io/iddfxd5j9l2o")
   metrics_image_path = "${local.registry_host}/oci-datadog-forwarder/metrics:latest"
   logs_image_path    = "${local.registry_host}/oci-datadog-forwarder/logs:latest"
@@ -39,5 +40,5 @@ locals {
   )
   
   # Simple subnet selection logic: use provided OCID or create new
-  subnet_id = var.subnet_ocid != "" ? var.subnet_ocid : module.vcn[0].subnet_id[local.subnet]
+  subnet_id = var.subnet_ocid != "" ? var.subnet_ocid : module.subnet[0].subnet_id[local.subnet]
 }
diff --git a/datadog-integration/modules/regional-stacks/main.tf b/datadog-integration/modules/regional-stacks/main.tf
index 41e2c79..6810e1c 100644
--- a/datadog-integration/modules/regional-stacks/main.tf
+++ b/datadog-integration/modules/regional-stacks/main.tf
@@ -17,6 +17,7 @@ resource "oci_functions_function" "logs_function" {
   display_name   = "dd-logs-forwarder"
   memory_in_mbs  = "1024"
   freeform_tags  = var.tags
+  defined_tags   = local.defined_tags_map
   image          = local.logs_image_path
   image_digest   = length(local.image_sha_logs) > 0 ? local.image_sha_logs : null
 
@@ -27,6 +28,7 @@ resource "oci_functions_function" "metrics_function" {
   display_name   = "dd-metrics-forwarder"
   memory_in_mbs  = "512"
   freeform_tags  = var.tags
+  defined_tags   = local.defined_tags_map
   image          = local.metrics_image_path
   image_digest   = length(local.image_sha_metrics) > 0 ? local.image_sha_metrics : null
 }
@@ -37,11 +39,28 @@ module "vcn" {
   version                  = "3.6.0"
   compartment_id           = var.compartment_ocid
   freeform_tags            = var.tags
+  defined_tags             = local.defined_tags_map
   vcn_cidrs                = ["10.0.0.0/16"]
   vcn_dns_label            = "ddvcnmodule"
   vcn_name                 = local.vcn_name
-  lockdown_default_seclist = false
+  lockdown_default_seclist  = false
+  subnets                  = {}
 
+  create_nat_gateway           = true
+  nat_gateway_display_name     = local.nat_gateway
+  create_service_gateway       = true
+  service_gateway_display_name = local.service_gateway
+}
+
+# Same VCN module's subnet submodule; we call it directly so we can pass defined_tags (parent VCN module doesn't).
+module "subnet" {
+  count          = var.subnet_ocid == "" ? 1 : 0
+  source        = "oracle-terraform-modules/vcn/oci//modules/subnet"
+  version       = "3.6.0"
+  compartment_id = var.compartment_ocid
+  vcn_id        = module.vcn[0].vcn_id
+  nat_route_id  = module.vcn[0].nat_route_id
+  ig_route_id   = module.vcn[0].ig_route_id
   subnets = {
     private = {
       cidr_block = "10.0.0.0/16"
@@ -49,17 +68,15 @@ module "vcn" {
       name       = local.subnet
     }
   }
-
-  create_nat_gateway           = true
-  nat_gateway_display_name     = local.nat_gateway
-  create_service_gateway       = true
-  service_gateway_display_name = local.service_gateway
+  freeform_tags = var.tags
+  defined_tags  = local.defined_tags_map
 }
 
 resource "oci_functions_application" "dd_function_app" {
   compartment_id = var.compartment_ocid
   display_name   = "dd-function-app"
   freeform_tags  = var.tags
+  defined_tags   = local.defined_tags_map
   shape          = "GENERIC_X86_ARM"
   subnet_ids = [
     local.subnet_id
diff --git a/datadog-integration/modules/regional-stacks/variables.tf b/datadog-integration/modules/regional-stacks/variables.tf
index c5ac420..28efdef 100644
--- a/datadog-integration/modules/regional-stacks/variables.tf
+++ b/datadog-integration/modules/regional-stacks/variables.tf
@@ -20,12 +20,18 @@ variable "datadog_site" {
 
 variable "tags" {
   type        = map(string)
-  description = "A map of tags to assign to the resource"
+  description = "A map of freeform tags to assign to the resource"
   default = {
     ownedby = "datadog"
   }
 }
 
+variable "defined_tags" {
+  type        = string
+  description = "JSON-encoded map of defined tags (namespace.key = value), e.g. \"{\\\"Namespace.Key\\\":\\\"value\\\"}\". Passed from parent stack."
+  default     = "{}"
+}
+
 variable "home_region" {
   type        = string
   description = "The name of the home region"
diff --git a/datadog-integration/regional_stack.tf b/datadog-integration/regional_stack.tf
index 8e81826..ff78ec1 100644
--- a/datadog-integration/regional_stack.tf
+++ b/datadog-integration/regional_stack.tf
@@ -65,7 +65,8 @@ resource "null_resource" "regional_stacks_create_apply" {
       --config-source ${path.module}/modules/regional-stacks/dd_regional_stack.zip  --variables '{"tenancy_ocid": "${var.tenancy_ocid}", "region": "${each.key}", \
       "compartment_ocid": "${module.compartment.id}", "datadog_site": "${var.datadog_site}", "api_key_secret_id": "${module.kms[0].api_key_secret_id}", \
       "home_region": "${local.home_region_name}", "region_key": "${local.subscribed_regions_map[each.key].region_key}", \
-      "subnet_ocid": "${lookup(local.region_to_subnet_ocid_map, each.key, "")}"}' \
+      "subnet_ocid": "${lookup(local.region_to_subnet_ocid_map, each.key, "")}", "defined_tags": ${jsonencode(jsonencode(local.defined_tags))}}' \
+      ${local.stack_create_defined_tags_flag} \
       --wait-for-state ACTIVE \
       --max-wait-seconds 120 \
       --wait-interval-seconds 5 \
@@ -85,7 +86,7 @@ resource "null_resource" "regional_stacks_create_apply" {
     JOB_ID=""
     for attempt in {1..5}; do
       echo "Attempting to create job (attempt $attempt/5)..."
-      if JOB_ID=$(oci resource-manager job create-apply-job --stack-id $STACK_ID $WAIT_COMMAND --execution-plan-strategy AUTO_APPROVED --region ${each.key} --query "data.id"); then
+      if JOB_ID=$(oci resource-manager job create-apply-job --stack-id $STACK_ID ${local.stack_create_defined_tags_flag} $WAIT_COMMAND --execution-plan-strategy AUTO_APPROVED --region ${each.key} --query "data.id"); then
         echo "Job created successfully: $JOB_ID for region ${each.key}"
         break
       else
@@ -115,8 +116,9 @@ resource "terraform_data" "regional_stacks_destroy" {
   depends_on = [null_resource.precheck_marker, terraform_data.regional_stack_zip, terraform_data.stack_digest]
   for_each   = local.target_regions_for_stacks
   input = {
-    compartment     = module.compartment.id
-    stack_digest_id = terraform_data.stack_digest.id
+    compartment       = module.compartment.id
+    stack_digest_id   = terraform_data.stack_digest.id
+    defined_tags_json = length(keys(local.compartment_defined_tags)) > 0 ? jsonencode(local.compartment_defined_tags) : ""
   }
 
   provisioner "local-exec" {
@@ -125,8 +127,8 @@ resource "terraform_data" "regional_stacks_destroy" {
     command     = <<EOT
     echo "Destroying........."
     STACK_NAME="datadog-regional-stack-${self.input.stack_digest_id}"
-    chmod +x ${path.module}/delete_stack.sh && ${path.module}/delete_stack.sh ${self.input.compartment} ${each.key} $STACK_NAME
-    
+    DEFINED_TAGS_JSON="${replace(replace(try(self.input.defined_tags_json, ""), "$", "\\$"), "\"", "\\\"")}"
+    chmod +x ${path.module}/delete_stack.sh && ${path.module}/delete_stack.sh ${self.input.compartment} ${each.key} "$STACK_NAME" "$DEFINED_TAGS_JSON"
     EOT
   }
 }
diff --git a/datadog-integration/schema.yaml b/datadog-integration/schema.yaml
index d947ea7..8d9a1ef 100644
--- a/datadog-integration/schema.yaml
+++ b/datadog-integration/schema.yaml
@@ -34,6 +34,7 @@ variableGroups:
       - ${compartment_id}
       - ${domain_id}
       - ${user_email}
+      - ${defined_tags}
 
 variables:
   choose_subnet:
@@ -170,3 +171,14 @@ variables:
         - ${show_advanced_options}
         - not:
             - ${choose_user}
+
+  defined_tags:
+    title: Defined tags
+    type: text
+    multiline: true
+    description: |
+      Defined tags to apply to all created resources. One entry per line in the format <strong>namespace.key:value</strong> (e.g. CostCenter.Environment:prod).
+      <strong>Datadog recommends leaving this blank unless your tenancy has mandatory tag defaults that apply to the compartment where Datadog resources will be created.</strong>
+    required: false
+    default: ""
+    visible: ${show_advanced_options}
diff --git a/datadog-integration/variables.tf b/datadog-integration/variables.tf
index eb7634b..3be2f5d 100644
--- a/datadog-integration/variables.tf
+++ b/datadog-integration/variables.tf
@@ -88,3 +88,9 @@ variable "user_email" {
   description = "Email address where you want OCI to send you notifications about the created user."
   default     = null
 }
+
+variable "defined_tags" {
+  type        = string
+  description = "Defined tags to apply to all created resources. One entry per line in the format namespace.key:value (e.g. CostCenter.Environment:prod). Leave blank unless your tenancy has mandatory tag defaults."
+  default     = ""
+}
\ No newline at end of file