diff --git a/README.md b/README.md
index 18c7c44..39ff985 100644
--- a/README.md
+++ b/README.md
@@ -43,6 +43,7 @@ To create a GitHub App and a GitHub App Installation:
         - Variables: Read and write
       - Organization permissions
         - Administration: Read and write
+        - Members: Read and write
       - Where can this GitHub App be installed?: _choose what suits you best_
     - **Create GitHub App**
   - _your app_
@@ -132,6 +133,9 @@ Create the configuration file:
 ```yaml
 ---
 organization: # OPTIONAL
+  members: # OPTIONAL, DEFAULT none
+    admins: # REQUIRED; GitHub usernames
+      - octocat
   environments: # OPTIONAL, DEFAULT none; added to every repository
     release:
       deployment_branches: # OPTIONAL, DEFAULT every branch
@@ -172,6 +176,12 @@ repositories:
       default-branch: ~ # opts out of the organization ruleset
 ```
 
+### Members
+
+`organization.members.admins` lists the organization owners. Only owners are managed: other members, teams and outside collaborators stay unmanaged. A listed user who is not a member yet is invited and stays pending until they accept. Every owner has `prevent_destroy`, so removing one from the list fails the plan; demote or remove an owner explicitly (`removed` block or `terraform state rm`). Existing memberships are imported, which needs the Terraform workspace named after the organization.
+
+Members need the App's organization Members permission, see [GitHub App](#github-app).
+
 ### Environments
 
 `organization.environments` is added to every repository's `environments`. A repository environment of the same name replaces the organization one wholesale (no key-level merge), `~` opts the repository out of it, other names are repository-only.
diff --git a/terraform/main.tf b/terraform/main.tf
index f0306df..2821a00 100644
--- a/terraform/main.tf
+++ b/terraform/main.tf
@@ -2,11 +2,14 @@ locals {
   config = try(yamldecode(file(var.config)), {})
 
   allowed_top_level_keys    = ["organization", "repositories"]
-  allowed_organization_keys = ["environments", "rulesets"]
+  allowed_organization_keys = ["members", "environments", "rulesets"]
+  allowed_members_keys      = ["admins"]
   allowed_repository_keys   = ["name", "description", "homepage_url", "topics", "is_template", "template", "environments", "rulesets"]
   allowed_environment_keys  = ["deployment_branches", "variables", "secrets", "reviewers"]
   allowed_ruleset_keys      = ["bypass_apps"]
 
+  organization_admins = try(toset(local.config.organization.members.admins), toset([]))
+
   organization_environments = try({ for name, environment in local.config.organization.environments : name => environment }, {})
   organization_rulesets     = try({ for name, ruleset in local.config.organization.rulesets : name => ruleset }, {})
 
@@ -31,3 +34,21 @@ module "repository" {
 
   repository = each.value
 }
+
+resource "github_membership" "admin" {
+  for_each = local.organization_admins
+
+  username = each.value
+  role     = "admin"
+
+  lifecycle {
+    prevent_destroy = true
+  }
+}
+
+# Keep until every workspace has applied this; the workspace is named after the organization.
+import {
+  for_each = local.organization_admins
+  to       = github_membership.admin[each.key]
+  id       = "${terraform.workspace}:${each.key}"
+}
diff --git a/terraform/tests/fixtures/members-admins-blank.yaml b/terraform/tests/fixtures/members-admins-blank.yaml
new file mode 100644
index 0000000..9b0c8de
--- /dev/null
+++ b/terraform/tests/fixtures/members-admins-blank.yaml
@@ -0,0 +1,8 @@
+---
+organization:
+  members:
+    admins:
+      - bruzina
+      - " "
+repositories:
+  - name: foo
diff --git a/terraform/tests/fixtures/members-admins-duplicate-case.yaml b/terraform/tests/fixtures/members-admins-duplicate-case.yaml
new file mode 100644
index 0000000..6b33bcc
--- /dev/null
+++ b/terraform/tests/fixtures/members-admins-duplicate-case.yaml
@@ -0,0 +1,8 @@
+---
+organization:
+  members:
+    admins:
+      - bruzina
+      - Bruzina
+repositories:
+  - name: foo
diff --git a/terraform/tests/fixtures/members-admins-empty.yaml b/terraform/tests/fixtures/members-admins-empty.yaml
new file mode 100644
index 0000000..a50491d
--- /dev/null
+++ b/terraform/tests/fixtures/members-admins-empty.yaml
@@ -0,0 +1,6 @@
+---
+organization:
+  members:
+    admins: []
+repositories:
+  - name: foo
diff --git a/terraform/tests/fixtures/members-admins-map.yaml b/terraform/tests/fixtures/members-admins-map.yaml
new file mode 100644
index 0000000..8244fc7
--- /dev/null
+++ b/terraform/tests/fixtures/members-admins-map.yaml
@@ -0,0 +1,7 @@
+---
+organization:
+  members:
+    admins:
+      bruzina: admin
+repositories:
+  - name: foo
diff --git a/terraform/tests/fixtures/members-null.yaml b/terraform/tests/fixtures/members-null.yaml
new file mode 100644
index 0000000..77dc8c4
--- /dev/null
+++ b/terraform/tests/fixtures/members-null.yaml
@@ -0,0 +1,5 @@
+---
+organization:
+  members: ~
+repositories:
+  - name: foo
diff --git a/terraform/tests/fixtures/members-unknown-key.yaml b/terraform/tests/fixtures/members-unknown-key.yaml
new file mode 100644
index 0000000..dad4a85
--- /dev/null
+++ b/terraform/tests/fixtures/members-unknown-key.yaml
@@ -0,0 +1,9 @@
+---
+organization:
+  members:
+    admins:
+      - bruzina
+    owners:
+      - octocat
+repositories:
+  - name: foo
diff --git a/terraform/tests/fixtures/members.yaml b/terraform/tests/fixtures/members.yaml
new file mode 100644
index 0000000..60674ab
--- /dev/null
+++ b/terraform/tests/fixtures/members.yaml
@@ -0,0 +1,8 @@
+---
+organization:
+  members:
+    admins:
+      - bruzina
+      - octocat
+repositories:
+  - name: foo
diff --git a/terraform/tests/members.tftest.hcl b/terraform/tests/members.tftest.hcl
new file mode 100644
index 0000000..32c764e
--- /dev/null
+++ b/terraform/tests/members.tftest.hcl
@@ -0,0 +1,94 @@
+mock_provider "github" {}
+
+override_resource {
+  target = github_membership.admin
+}
+
+run "members" {
+  command = plan
+
+  variables {
+    config = "tests/fixtures/members.yaml"
+  }
+
+  assert {
+    condition     = keys(github_membership.admin) == ["bruzina", "octocat"] && alltrue([for m in github_membership.admin : m.role == "admin"])
+    error_message = "Expected admins bruzina and octocat."
+  }
+}
+
+run "no_members" {
+  command = plan
+
+  variables {
+    config = "tests/fixtures/one-repository.yaml"
+  }
+
+  assert {
+    condition     = length(github_membership.admin) == 0
+    error_message = "Expected no memberships."
+  }
+}
+
+run "members_null" {
+  command = plan
+
+  variables {
+    config = "tests/fixtures/members-null.yaml"
+  }
+
+  assert {
+    condition     = length(github_membership.admin) == 0
+    error_message = "Expected no memberships."
+  }
+}
+
+run "members_unknown_key" {
+  command = plan
+
+  variables {
+    config = "tests/fixtures/members-unknown-key.yaml"
+  }
+
+  expect_failures = [var.config]
+}
+
+run "members_admins_empty" {
+  command = plan
+
+  variables {
+    config = "tests/fixtures/members-admins-empty.yaml"
+  }
+
+  expect_failures = [var.config]
+}
+
+run "members_admins_map" {
+  command = plan
+
+  variables {
+    config = "tests/fixtures/members-admins-map.yaml"
+  }
+
+  expect_failures = [var.config]
+}
+
+run "members_admins_blank" {
+  command = plan
+
+  variables {
+    config = "tests/fixtures/members-admins-blank.yaml"
+  }
+
+  expect_failures = [var.config]
+}
+
+run "members_admins_duplicate_case" {
+  command = plan
+
+  variables {
+    config = "tests/fixtures/members-admins-duplicate-case.yaml"
+  }
+
+  expect_failures = [var.config]
+}
diff --git a/terraform/tests/test-yaml.tftest.hcl b/terraform/tests/test-yaml.tftest.hcl
index c792cdd..c696680 100644
--- a/terraform/tests/test-yaml.tftest.hcl
+++ b/terraform/tests/test-yaml.tftest.hcl
@@ -6,6 +6,10 @@ mock_provider "github" {
   }
 }
 
+override_resource {
+  target = github_membership.admin
+}
+
 run "test_yaml" {
   command = apply
 
@@ -13,6 +17,11 @@ run "test_yaml" {
     config = "../test.yaml"
   }
 
+  assert {
+    condition     = keys(github_membership.admin) == ["bruzina"]
+    error_message = "Expected admin bruzina."
+  }
+
   assert {
     condition     = keys(module.repository) == [".github", "template", "template-use"]
     error_message = "Expected repositories .github, template, template-use."
diff --git a/terraform/variables.tf b/terraform/variables.tf
index 0434d7e..8e30390 100644
--- a/terraform/variables.tf
+++ b/terraform/variables.tf
@@ -37,6 +37,10 @@ variable "config" {
     condition     = try(yamldecode(file(var.config)).organization == null, true) || try(length(setsubtract(keys(yamldecode(file(var.config)).organization), local.allowed_organization_keys)) == 0, false)
     error_message = "File ${var.config}: organization must be a map with key(s) ${join(", ", local.allowed_organization_keys)}; unknown: ${try(join(", ", setsubtract(keys(yamldecode(file(var.config)).organization), local.allowed_organization_keys)), "")}"
   }
+  validation {
+    condition     = try(yamldecode(file(var.config)).organization.members == null, true) || try(length(setsubtract(keys(yamldecode(file(var.config)).organization.members), local.allowed_members_keys)) == 0 && length(concat(yamldecode(file(var.config)).organization.members.admins, [])) > 0 && alltrue([for u in yamldecode(file(var.config)).organization.members.admins : trimspace(u) != ""]) && length(distinct([for u in yamldecode(file(var.config)).organization.members.admins : lower(u)])) == length(yamldecode(file(var.config)).organization.members.admins), false)
+    error_message = "File ${var.config}: organization.members must be a map of ${join(", ", local.allowed_members_keys)}; admins must be a non-empty list of unique GitHub usernames."
+  }
   validation {
     condition     = try(length(flatten([for s in concat([{ label = "organization", environments = try(yamldecode(file(var.config)).organization.environments, null), opt_out = false }], [for r in yamldecode(file(var.config)).repositories : { label = r.name, environments = try(r.environments, null), opt_out = true }]) : s.environments == null ? [] : !can(keys(s.environments)) ? ["${s.label}.environments"] : [for n, e in s.environments : "${s.label}.environments.${n}" if !(s.opt_out && e == null) && !try(length(setsubtract(keys(e), local.allowed_environment_keys)) == 0, false)]])) == 0, true)
     error_message = "Invalid environment(s) in ${var.config}: ${try(join(", ", flatten([for s in concat([{ label = "organization", environments = try(yamldecode(file(var.config)).organization.environments, null), opt_out = false }], [for r in yamldecode(file(var.config)).repositories : { label = r.name, environments = try(r.environments, null), opt_out = true }]) : s.environments == null ? [] : !can(keys(s.environments)) ? ["${s.label}.environments"] : [for n, e in s.environments : "${s.label}.environments.${n}" if !(s.opt_out && e == null) && !try(length(setsubtract(keys(e), local.allowed_environment_keys)) == 0, false)]])), "")}; each must be a map of ${join(", ", local.allowed_environment_keys)}, or ~ under a repository to opt out of an organization environment."
diff --git a/test.yaml b/test.yaml
index 50d8383..7996c3e 100644
--- a/test.yaml
+++ b/test.yaml
@@ -1,5 +1,8 @@
 ---
 organization:
+  members:
+    admins:
+      - bruzina
   environments:
     release:
       deployment_branches: