diff --git a/backend/alembic/versions/014_add_audit_logs.py b/backend/alembic/versions/014_add_audit_logs.py
new file mode 100644
index 00000000..cb1d2b45
--- /dev/null
+++ b/backend/alembic/versions/014_add_audit_logs.py
@@ -0,0 +1,45 @@
+"""add audit_logs table
+
+Revision ID: 014
+Revises: 013
+Create Date: 2026-02-05
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.dialects.postgresql import UUID, JSONB
+
+
+# revision identifiers, used by Alembic.
+revision: str = '014'
+down_revision: Union[str, None] = '013'
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    op.create_table(
+        'audit_logs',
+        sa.Column('id', UUID(as_uuid=True), primary_key=True),
+        sa.Column('user_id', UUID(as_uuid=True), sa.ForeignKey('users.id'), nullable=False),
+        sa.Column('action', sa.String(50), nullable=False),
+        sa.Column('resource_type', sa.String(50), nullable=False),
+        sa.Column('resource_id', UUID(as_uuid=True), nullable=True),
+        sa.Column('details', JSONB, nullable=True),
+        sa.Column('ip_address', sa.String(45), nullable=True),
+        sa.Column('created_at', sa.DateTime(timezone=True), server_default=sa.func.now()),
+    )
+    op.create_index('ix_audit_logs_user_id', 'audit_logs', ['user_id'])
+    op.create_index('ix_audit_logs_action', 'audit_logs', ['action'])
+    op.create_index('ix_audit_logs_resource_type', 'audit_logs', ['resource_type'])
+    op.create_index('ix_audit_logs_created_at', 'audit_logs', ['created_at'])
+
+
+def downgrade() -> None:
+    op.drop_index('ix_audit_logs_created_at', table_name='audit_logs')
+    op.drop_index('ix_audit_logs_resource_type', table_name='audit_logs')
+    op.drop_index('ix_audit_logs_action', table_name='audit_logs')
+    op.drop_index('ix_audit_logs_user_id', table_name='audit_logs')
+    op.drop_table('audit_logs')
diff --git a/backend/app/api/endpoints/admin.py b/backend/app/api/endpoints/admin.py
index ec03d441..daa04166 100644
--- a/backend/app/api/endpoints/admin.py
+++ b/backend/app/api/endpoints/admin.py
@@ -5,6 +5,7 @@ from sqlalchemy.ext.asyncio import AsyncSession
 from sqlalchemy import select, func
 
 from app.core.database import get_db
+from app.core.audit import log_audit
 from app.models.user import User
 from app.schemas.user import UserResponse, RoleUpdate, TeamAdminUpdate
 from app.api.deps import require_admin
@@ -81,7 +82,10 @@ async def update_user_role(
             detail="Cannot change your own role"
         )
 
+    old_role = user.role
     user.role = role_data.role
+    await log_audit(db, current_user.id, "user.role_change", "user", user.id,
+                    {"old_role": old_role, "new_role": role_data.role})
     await db.commit()
     await db.refresh(user)
     return user
@@ -111,6 +115,8 @@ async def toggle_team_admin(
         )
 
     user.is_team_admin = data.is_team_admin
+    await log_audit(db, current_user.id, "user.team_admin_toggle", "user", user.id,
+                    {"is_team_admin": data.is_team_admin})
     await db.commit()
     await db.refresh(user)
     return user
@@ -139,6 +145,7 @@ async def deactivate_user(
         )
 
     user.is_active = False
+    await log_audit(db, current_user.id, "user.deactivate", "user", user.id)
     await db.commit()
     await db.refresh(user)
     return user
@@ -161,6 +168,7 @@ async def activate_user(
         )
 
     user.is_active = True
+    await log_audit(db, current_user.id, "user.activate", "user", user.id)
     await db.commit()
     await db.refresh(user)
     return user
diff --git a/backend/app/api/endpoints/trees.py b/backend/app/api/endpoints/trees.py
index 858f1490..a246e8ab 100644
--- a/backend/app/api/endpoints/trees.py
+++ b/backend/app/api/endpoints/trees.py
@@ -14,6 +14,7 @@ from app.models.folder import UserFolder
 from app.schemas.tree import TreeCreate, TreeUpdate, TreeResponse, TreeListResponse, CategoryInfo
 from app.api.deps import get_current_active_user, require_engineer_or_admin, require_admin
 from app.core.permissions import can_edit_tree, can_access_tree
+from app.core.audit import log_audit
 
 router = APIRouter(prefix="/trees", tags=["trees"])
 
@@ -518,5 +519,7 @@ async def delete_tree(
         )
 
     tree.is_active = False
+    await log_audit(db, current_user.id, "tree.delete", "tree", tree.id,
+                    {"tree_name": tree.name})
     await db.commit()
     return None
diff --git a/backend/app/core/audit.py b/backend/app/core/audit.py
new file mode 100644
index 00000000..58ecd620
--- /dev/null
+++ b/backend/app/core/audit.py
@@ -0,0 +1,24 @@
+"""Centralized audit logging for admin and destructive actions."""
+from uuid import UUID
+from typing import Optional
+from sqlalchemy.ext.asyncio import AsyncSession
+from app.models.audit_log import AuditLog
+
+
+async def log_audit(
+    db: AsyncSession,
+    user_id: UUID,
+    action: str,
+    resource_type: str,
+    resource_id: Optional[UUID] = None,
+    details: Optional[dict] = None,
+) -> None:
+    """Record an audit log entry. Does not commit — piggybacks on the caller's commit."""
+    entry = AuditLog(
+        user_id=user_id,
+        action=action,
+        resource_type=resource_type,
+        resource_id=resource_id,
+        details=details,
+    )
+    db.add(entry)
diff --git a/backend/app/models/__init__.py b/backend/app/models/__init__.py
index b43bb54e..28cb75bc 100644
--- a/backend/app/models/__init__.py
+++ b/backend/app/models/__init__.py
@@ -10,6 +10,7 @@ from .folder import UserFolder, user_folder_trees
 from .step_category import StepCategory
 from .step_library import StepLibrary, StepRating, StepUsageLog
 from .refresh_token import RefreshToken
+from .audit_log import AuditLog
 
 __all__ = [
     "User",
@@ -28,4 +29,5 @@ __all__ = [
     "StepRating",
     "StepUsageLog",
     "RefreshToken",
+    "AuditLog",
 ]
diff --git a/backend/app/models/audit_log.py b/backend/app/models/audit_log.py
new file mode 100644
index 00000000..25fa669e
--- /dev/null
+++ b/backend/app/models/audit_log.py
@@ -0,0 +1,35 @@
+import uuid
+from datetime import datetime, timezone
+from typing import Optional
+from sqlalchemy import String, DateTime, ForeignKey
+from sqlalchemy.orm import Mapped, mapped_column
+from sqlalchemy.dialects.postgresql import UUID, JSONB
+from app.core.database import Base
+
+
+class AuditLog(Base):
+    __tablename__ = "audit_logs"
+
+    id: Mapped[uuid.UUID] = mapped_column(
+        UUID(as_uuid=True),
+        primary_key=True,
+        default=uuid.uuid4
+    )
+    user_id: Mapped[uuid.UUID] = mapped_column(
+        UUID(as_uuid=True),
+        ForeignKey("users.id"),
+        nullable=False,
+        index=True
+    )
+    action: Mapped[str] = mapped_column(String(50), nullable=False, index=True)
+    resource_type: Mapped[str] = mapped_column(String(50), nullable=False, index=True)
+    resource_id: Mapped[Optional[uuid.UUID]] = mapped_column(
+        UUID(as_uuid=True),
+        nullable=True
+    )
+    details: Mapped[Optional[dict]] = mapped_column(JSONB, nullable=True)
+    ip_address: Mapped[Optional[str]] = mapped_column(String(45), nullable=True)
+    created_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True),
+        default=lambda: datetime.now(timezone.utc)
+    )
diff --git a/backend/tests/test_admin.py b/backend/tests/test_admin.py
index 8d2a3d4b..aebc9ebc 100644
--- a/backend/tests/test_admin.py
+++ b/backend/tests/test_admin.py
@@ -2,6 +2,9 @@
 
 import pytest
 from httpx import AsyncClient
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+from app.models.audit_log import AuditLog
 
 
 class TestAdminEndpoints:
@@ -127,3 +130,42 @@ class TestAdminEndpoints:
         )
         assert response.status_code == 400
         assert "own account" in response.json()["detail"].lower()
+
+    @pytest.mark.asyncio
+    async def test_audit_log_created_on_role_change(
+        self, client: AsyncClient, admin_auth_headers: dict, test_user: dict, test_db: AsyncSession
+    ):
+        """Test that changing a user's role creates an audit log entry."""
+        user_id = test_user["user_data"]["id"]
+        await client.put(
+            f"/api/v1/admin/users/{user_id}/role",
+            json={"role": "viewer"},
+            headers=admin_auth_headers
+        )
+
+        result = await test_db.execute(
+            select(AuditLog).where(AuditLog.action == "user.role_change")
+        )
+        log = result.scalar_one_or_none()
+        assert log is not None
+        assert str(log.resource_id) == user_id
+        assert log.details["old_role"] == "engineer"
+        assert log.details["new_role"] == "viewer"
+
+    @pytest.mark.asyncio
+    async def test_audit_log_created_on_deactivate(
+        self, client: AsyncClient, admin_auth_headers: dict, test_user: dict, test_db: AsyncSession
+    ):
+        """Test that deactivating a user creates an audit log entry."""
+        user_id = test_user["user_data"]["id"]
+        await client.put(
+            f"/api/v1/admin/users/{user_id}/deactivate",
+            headers=admin_auth_headers
+        )
+
+        result = await test_db.execute(
+            select(AuditLog).where(AuditLog.action == "user.deactivate")
+        )
+        log = result.scalar_one_or_none()
+        assert log is not None
+        assert str(log.resource_id) == user_id