diff --git a/src/dstack/_internal/server/migrations/versions/06e977bc61c7_add_usermodel_deleted_and_original_name.py b/src/dstack/_internal/server/migrations/versions/06e977bc61c7_add_usermodel_deleted_and_original_name.py
new file mode 100644
index 000000000..434c0e286
--- /dev/null
+++ b/src/dstack/_internal/server/migrations/versions/06e977bc61c7_add_usermodel_deleted_and_original_name.py
@@ -0,0 +1,41 @@
+"""Add UserModel.deleted and original_name
+
+Revision ID: 06e977bc61c7
+Revises: 7d1ec2b920ac
+Create Date: 2025-11-26 11:43:34.825686
+
+"""
+
+import sqlalchemy as sa
+from alembic import op
+
+# revision identifiers, used by Alembic.
+revision = "06e977bc61c7"
+down_revision = "7d1ec2b920ac"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    # ### commands auto generated by Alembic - please adjust! ###
+    with op.batch_alter_table("users", schema=None) as batch_op:
+        batch_op.add_column(
+            sa.Column("deleted", sa.Boolean(), server_default=sa.false(), nullable=False)
+        )
+        batch_op.add_column(sa.Column("original_name", sa.String(length=50), nullable=True))
+
+    with op.batch_alter_table("projects", schema=None) as batch_op:
+        batch_op.add_column(sa.Column("original_name", sa.String(length=50), nullable=True))
+    # ### end Alembic commands ###
+
+
+def downgrade() -> None:
+    # ### commands auto generated by Alembic - please adjust! ###
+    with op.batch_alter_table("users", schema=None) as batch_op:
+        batch_op.drop_column("original_name")
+        batch_op.drop_column("deleted")
+
+    with op.batch_alter_table("projects", schema=None) as batch_op:
+        batch_op.drop_column("original_name")
+
+    # ### end Alembic commands ###
diff --git a/src/dstack/_internal/server/models.py b/src/dstack/_internal/server/models.py
index e88f83d59..04185762a 100644
--- a/src/dstack/_internal/server/models.py
+++ b/src/dstack/_internal/server/models.py
@@ -190,6 +190,9 @@ class UserModel(BaseModel):
     global_role: Mapped[GlobalRole] = mapped_column(EnumAsString(GlobalRole, 100))
     # deactivated users cannot access API
     active: Mapped[bool] = mapped_column(Boolean, default=True)
+    deleted: Mapped[bool] = mapped_column(Boolean, server_default=false())
+    # `original_name` stores the name of a deleted user, while `name` is changed to a unique generated value.
+    original_name: Mapped[Optional[str]] = mapped_column(String(50), nullable=True)
 
     # SSH keys can be null for users created before 0.19.33.
     # Keys for those users are being gradually generated on /get_my_user calls.
@@ -212,8 +215,10 @@ class ProjectModel(BaseModel):
     )
     name: Mapped[str] = mapped_column(String(50), unique=True)
     created_at: Mapped[datetime] = mapped_column(NaiveDateTime, default=get_current_datetime)
-    deleted: Mapped[bool] = mapped_column(Boolean, default=False)
     is_public: Mapped[bool] = mapped_column(Boolean, default=False)
+    deleted: Mapped[bool] = mapped_column(Boolean, default=False)
+    # `original_name` stores the name of a deleted project, while `name` is changed to a unique generated value.
+    original_name: Mapped[Optional[str]] = mapped_column(String(50), nullable=True)
 
     owner_id: Mapped[uuid.UUID] = mapped_column(ForeignKey("users.id", ondelete="CASCADE"))
     owner: Mapped[UserModel] = relationship(lazy="joined")
diff --git a/src/dstack/_internal/server/services/projects.py b/src/dstack/_internal/server/services/projects.py
index 330fcceb4..cc6c37401 100644
--- a/src/dstack/_internal/server/services/projects.py
+++ b/src/dstack/_internal/server/services/projects.py
@@ -1,3 +1,4 @@
+import secrets
 import uuid
 from typing import Awaitable, Callable, List, Optional, Tuple
 
@@ -194,28 +195,36 @@ async def delete_projects(
             raise ServerClientError("Cannot delete the only project")
 
     res = await session.execute(
-        select(ProjectModel.id).where(ProjectModel.name.in_(projects_names))
+        select(ProjectModel)
+        .where(
+            ProjectModel.name.in_(projects_names),
+            ProjectModel.deleted == False,
+        )
+        .options(load_only(ProjectModel.id, ProjectModel.name))
     )
-    project_ids = res.scalars().all()
-    if len(project_ids) != len(projects_names):
+    projects = res.scalars().all()
+    if len(projects) != len(projects_names):
         raise ServerClientError("Failed to delete non-existent projects")
 
-    for project_id in project_ids:
+    for p in projects:
         # FIXME: The checks are not under lock,
         # so there can be dangling active resources due to race conditions.
-        await _check_project_has_active_resources(session=session, project_id=project_id)
+        await _check_project_has_active_resources(session=session, project_id=p.id)
 
     timestamp = str(int(get_current_datetime().timestamp()))
-    new_project_name = "_deleted_" + timestamp + ProjectModel.name
-    await session.execute(
-        update(ProjectModel)
-        .where(ProjectModel.name.in_(projects_names))
-        .values(
-            deleted=True,
-            name=new_project_name,
+    updates = []
+    for p in projects:
+        updates.append(
+            {
+                "id": p.id,
+                "name": f"_deleted_{timestamp}_{secrets.token_hex(8)}",
+                "original_name": p.name,
+                "deleted": True,
+            }
         )
-    )
+    await session.execute(update(ProjectModel), updates)
     await session.commit()
+    logger.info("Deleted projects %s by user %s", projects_names, user.name)
 
 
 async def set_project_members(
@@ -244,12 +253,16 @@ async def set_project_members(
         }
         if new_admins_members != current_admins_members:
             raise ForbiddenError("Access denied: changing project admins")
+
     # FIXME: potentially long write transaction
     # clear_project_members() issues DELETE without commit
     await clear_project_members(session=session, project=project)
     names = [m.username for m in members]
     res = await session.execute(
-        select(UserModel).where((UserModel.name.in_(names)) | (UserModel.email.in_(names)))
+        select(UserModel).where(
+            (UserModel.name.in_(names)) | (UserModel.email.in_(names)),
+            UserModel.deleted == False,
+        )
     )
     users = res.scalars().all()
     username_to_user = {user.name: user for user in users}
@@ -311,7 +324,10 @@ async def add_project_members(
             raise ForbiddenError("Access denied: can only join public projects as user role")
 
     res = await session.execute(
-        select(UserModel).where((UserModel.name.in_(usernames)) | (UserModel.email.in_(usernames)))
+        select(UserModel).where(
+            (UserModel.name.in_(usernames)) | (UserModel.email.in_(usernames)),
+            UserModel.deleted == False,
+        )
     )
     users_found = res.scalars().all()
 
@@ -700,7 +716,10 @@ async def remove_project_members(
             raise ForbiddenError("Access denied: insufficient permissions to remove members")
 
     res = await session.execute(
-        select(UserModel).where((UserModel.name.in_(usernames)) | (UserModel.email.in_(usernames)))
+        select(UserModel).where(
+            (UserModel.name.in_(usernames)) | (UserModel.email.in_(usernames)),
+            UserModel.deleted == False,
+        )
     )
     users_found = res.scalars().all()
 
diff --git a/src/dstack/_internal/server/services/users.py b/src/dstack/_internal/server/services/users.py
index 9fdbe3b4e..aed0a23de 100644
--- a/src/dstack/_internal/server/services/users.py
+++ b/src/dstack/_internal/server/services/users.py
@@ -1,12 +1,14 @@
 import hashlib
 import os
 import re
+import secrets
 import uuid
 from typing import Awaitable, Callable, List, Optional, Tuple
 
 from sqlalchemy import delete, select, update
 from sqlalchemy import func as safunc
 from sqlalchemy.ext.asyncio import AsyncSession
+from sqlalchemy.orm import load_only
 
 from dstack._internal.core.errors import ResourceExistsError, ServerClientError
 from dstack._internal.core.models.users import (
@@ -17,11 +19,11 @@
     UserTokenCreds,
     UserWithCreds,
 )
-from dstack._internal.server.models import DecryptedString, UserModel
+from dstack._internal.server.models import DecryptedString, MemberModel, UserModel
 from dstack._internal.server.services.permissions import get_default_permissions
 from dstack._internal.server.utils.routers import error_forbidden
 from dstack._internal.utils import crypto
-from dstack._internal.utils.common import run_async
+from dstack._internal.utils.common import get_current_datetime, get_or_error, run_async
 from dstack._internal.utils.logging import get_logger
 
 logger = get_logger(__name__)
@@ -53,8 +55,12 @@ async def list_users_for_user(
 
 async def list_all_users(
     session: AsyncSession,
+    include_deleted: bool = False,
 ) -> List[User]:
-    res = await session.execute(select(UserModel))
+    filters = []
+    if not include_deleted:
+        filters.append(UserModel.deleted == False)
+    res = await session.execute(select(UserModel).where(*filters))
     user_models = res.scalars().all()
     user_models = sorted(user_models, key=lambda u: u.created_at)
     return [user_model_to_user(u) for u in user_models]
@@ -116,7 +122,10 @@ async def update_user(
 ) -> UserModel:
     await session.execute(
         update(UserModel)
-        .where(UserModel.name == username)
+        .where(
+            UserModel.name == username,
+            UserModel.deleted == False,
+        )
         .values(
             global_role=global_role,
             email=email,
@@ -138,7 +147,10 @@ async def refresh_ssh_key(
     private_bytes, public_bytes = await run_async(crypto.generate_rsa_key_pair_bytes, username)
     await session.execute(
         update(UserModel)
-        .where(UserModel.name == username)
+        .where(
+            UserModel.name == username,
+            UserModel.deleted == False,
+        )
         .values(
             ssh_private_key=private_bytes.decode(),
             ssh_public_key=public_bytes.decode(),
@@ -158,7 +170,10 @@ async def refresh_user_token(
     new_token = str(uuid.uuid4())
     await session.execute(
         update(UserModel)
-        .where(UserModel.name == username)
+        .where(
+            UserModel.name == username,
+            UserModel.deleted == False,
+        )
         .values(
             token=DecryptedString(plaintext=new_token),
             token_hash=get_token_hash(new_token),
@@ -173,7 +188,37 @@ async def delete_users(
     user: UserModel,
     usernames: List[str],
 ):
-    await session.execute(delete(UserModel).where(UserModel.name.in_(usernames)))
+    if _ADMIN_USERNAME in usernames:
+        raise ServerClientError("User 'admin' cannot be deleted")
+
+    res = await session.execute(
+        select(UserModel)
+        .where(
+            UserModel.name.in_(usernames),
+            UserModel.deleted == False,
+        )
+        .options(load_only(UserModel.id, UserModel.name))
+    )
+    users = res.scalars().all()
+    if len(users) != len(usernames):
+        raise ServerClientError("Failed to delete non-existent users")
+
+    user_ids = [u.id for u in users]
+    timestamp = str(int(get_current_datetime().timestamp()))
+    updates = []
+    for u in users:
+        updates.append(
+            {
+                "id": u.id,
+                "name": f"_deleted_{timestamp}_{secrets.token_hex(8)}",
+                "original_name": u.name,
+                "deleted": True,
+                "active": False,
+            }
+        )
+    await session.execute(update(UserModel), updates)
+    await session.execute(delete(MemberModel).where(MemberModel.user_id.in_(user_ids)))
+    # Projects are not deleted automatically if owners are deleted.
     await session.commit()
     logger.info("Deleted users %s by user %s", usernames, user.name)
 
@@ -183,7 +228,7 @@ async def get_user_model_by_name(
     username: str,
     ignore_case: bool = False,
 ) -> Optional[UserModel]:
-    filters = []
+    filters = [UserModel.deleted == False]
     if ignore_case:
         filters.append(safunc.lower(UserModel.name) == safunc.lower(username))
     else:
@@ -192,9 +237,14 @@ async def get_user_model_by_name(
     return res.scalar()
 
 
-async def get_user_model_by_name_or_error(session: AsyncSession, username: str) -> UserModel:
-    res = await session.execute(select(UserModel).where(UserModel.name == username))
-    return res.scalar_one()
+async def get_user_model_by_name_or_error(
+    session: AsyncSession,
+    username: str,
+    ignore_case: bool = False,
+) -> UserModel:
+    return get_or_error(
+        await get_user_model_by_name(session=session, username=username, ignore_case=ignore_case)
+    )
 
 
 async def log_in_with_token(session: AsyncSession, token: str) -> Optional[UserModel]:
@@ -203,6 +253,7 @@ async def log_in_with_token(session: AsyncSession, token: str) -> Optional[UserM
         select(UserModel).where(
             UserModel.token_hash == token_hash,
             UserModel.active == True,
+            UserModel.deleted == False,
         )
     )
     user = res.scalar()
diff --git a/src/dstack/_internal/server/testing/common.py b/src/dstack/_internal/server/testing/common.py
index 883ce1453..9c9585982 100644
--- a/src/dstack/_internal/server/testing/common.py
+++ b/src/dstack/_internal/server/testing/common.py
@@ -135,6 +135,7 @@ async def create_user(
     ssh_public_key: Optional[str] = None,
     ssh_private_key: Optional[str] = None,
     active: bool = True,
+    deleted: bool = False,
 ) -> UserModel:
     if token is None:
         token = str(uuid.uuid4())
@@ -148,6 +149,7 @@ async def create_user(
         ssh_public_key=ssh_public_key,
         ssh_private_key=ssh_private_key,
         active=active,
+        deleted=deleted,
     )
     session.add(user)
     await session.commit()
diff --git a/src/tests/_internal/server/routers/test_projects.py b/src/tests/_internal/server/routers/test_projects.py
index d3b042696..8e21957f5 100644
--- a/src/tests/_internal/server/routers/test_projects.py
+++ b/src/tests/_internal/server/routers/test_projects.py
@@ -472,9 +472,12 @@ async def test_cannot_delete_the_only_project(
 
     @pytest.mark.asyncio
     @pytest.mark.parametrize("test_db", ["sqlite", "postgres"], indirect=True)
-    async def test_deletes_projects(self, test_db, session: AsyncSession, client: AsyncClient):
+    @pytest.mark.parametrize("project_name", ["project1", "a" * 50])
+    async def test_deletes_projects(
+        self, test_db, session: AsyncSession, client: AsyncClient, project_name: str
+    ):
         user = await create_user(session=session, global_role=GlobalRole.USER)
-        project1 = await create_project(session=session, owner=user, name="project1")
+        project1 = await create_project(session=session, owner=user, name=project_name)
         await add_project_member(
             session=session, project=project1, user=user, project_role=ProjectRole.ADMIN
         )
diff --git a/src/tests/_internal/server/routers/test_users.py b/src/tests/_internal/server/routers/test_users.py
index 54da63803..8b8c7ca2a 100644
--- a/src/tests/_internal/server/routers/test_users.py
+++ b/src/tests/_internal/server/routers/test_users.py
@@ -8,9 +8,20 @@
 from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncSession
 
+from dstack._internal.core.models.projects import ProjectRole
+from dstack._internal.core.models.runs import JobStatus, RunStatus
 from dstack._internal.core.models.users import GlobalRole
-from dstack._internal.server.models import UserModel
-from dstack._internal.server.testing.common import create_user, get_auth_headers
+from dstack._internal.server.models import MemberModel, UserModel
+from dstack._internal.server.services.projects import add_project_member
+from dstack._internal.server.testing.common import (
+    create_job,
+    create_probe,
+    create_project,
+    create_repo,
+    create_run,
+    create_user,
+    get_auth_headers,
+)
 
 
 class TestListUsers:
@@ -22,7 +33,9 @@ async def test_returns_40x_if_not_authenticated(self, test_db, client: AsyncClie
 
     @pytest.mark.asyncio
     @pytest.mark.parametrize("test_db", ["sqlite", "postgres"], indirect=True)
-    async def test_admins_see_all_users(self, test_db, session: AsyncSession, client: AsyncClient):
+    async def test_admins_see_all_non_deleted_users(
+        self, test_db, session: AsyncSession, client: AsyncClient
+    ):
         admin = await create_user(
             session=session,
             name="admin",
@@ -35,6 +48,13 @@ async def test_admins_see_all_users(self, test_db, session: AsyncSession, client
             created_at=datetime(2023, 1, 2, 3, 4, tzinfo=timezone.utc),
             global_role=GlobalRole.USER,
         )
+        await create_user(
+            session=session,
+            name="deleted_user",
+            created_at=datetime(2023, 1, 2, 3, 4, tzinfo=timezone.utc),
+            global_role=GlobalRole.USER,
+            deleted=True,
+        )
         response = await client.post("/api/users/list", headers=get_auth_headers(admin.token))
         assert response.status_code in [200]
         assert response.json() == [
@@ -360,9 +380,12 @@ async def test_returns_40x_if_not_authenticated(self, test_db, client: AsyncClie
 
     @pytest.mark.asyncio
     @pytest.mark.parametrize("test_db", ["sqlite", "postgres"], indirect=True)
-    async def test_deletes_users(self, test_db, session: AsyncSession, client: AsyncClient):
+    @pytest.mark.parametrize("username", ["test", "a" * 50])
+    async def test_deletes_users(
+        self, test_db, session: AsyncSession, client: AsyncClient, username: str
+    ):
         admin = await create_user(name="admin", session=session)
-        user = await create_user(name="test", session=session)
+        user = await create_user(name=username, session=session)
         response = await client.post(
             "/api/users/delete",
             headers=get_auth_headers(admin.token),
@@ -372,6 +395,78 @@ async def test_deletes_users(self, test_db, session: AsyncSession, client: Async
         res = await session.execute(select(UserModel).where(UserModel.name == user.name))
         assert len(res.scalars().all()) == 0
 
+    @pytest.mark.asyncio
+    @pytest.mark.parametrize("test_db", ["sqlite", "postgres"], indirect=True)
+    async def test_returns_400_if_users_not_exist(
+        self, test_db, session: AsyncSession, client: AsyncClient
+    ):
+        admin = await create_user(name="admin", session=session)
+        user1 = await create_user(name="test1", session=session)
+        user2 = await create_user(name="test2", session=session)
+        response = await client.post(
+            "/api/users/delete",
+            headers=get_auth_headers(admin.token),
+            json={"users": [user1.name, "non_existing_user"]},
+        )
+        assert response.status_code == 400
+        response = await client.post(
+            "/api/users/delete",
+            headers=get_auth_headers(admin.token),
+            json={"users": [user1.name, user2.name]},
+        )
+        assert response.status_code == 200
+
+    @pytest.mark.asyncio
+    @pytest.mark.parametrize("test_db", ["sqlite", "postgres"], indirect=True)
+    @pytest.mark.usefixtures("image_config_mock")
+    async def test_deletes_user_with_resources(
+        self, test_db, session: AsyncSession, client: AsyncClient
+    ):
+        admin = await create_user(name="admin", session=session)
+        user = await create_user(name="temp", session=session, global_role=GlobalRole.USER)
+        project = await create_project(session=session, owner=user)
+        repo = await create_repo(session=session, project_id=project.id)
+        run = await create_run(
+            session=session,
+            project=project,
+            repo=repo,
+            user=user,
+            status=RunStatus.RUNNING,
+        )
+        job = await create_job(session=session, run=run, status=JobStatus.RUNNING)
+        await create_probe(session=session, job=job)
+        response = await client.post(
+            "/api/users/delete",
+            headers=get_auth_headers(admin.token),
+            json={"users": [user.name]},
+        )
+        assert response.status_code == 200
+        res = await session.execute(select(UserModel).where(UserModel.name == user.name))
+        assert res.scalar() is None
+
+    @pytest.mark.asyncio
+    @pytest.mark.parametrize("test_db", ["sqlite", "postgres"], indirect=True)
+    @pytest.mark.usefixtures("image_config_mock")
+    async def test_deleting_users_deletes_members(
+        self, test_db, session: AsyncSession, client: AsyncClient
+    ):
+        admin = await create_user(name="admin", session=session)
+        user = await create_user(name="temp", session=session, global_role=GlobalRole.USER)
+        project = await create_project(session=session, owner=user)
+        await add_project_member(
+            session=session, project=project, user=user, project_role=ProjectRole.USER
+        )
+        response = await client.post(
+            "/api/users/delete",
+            headers=get_auth_headers(admin.token),
+            json={"users": [user.name]},
+        )
+        assert response.status_code == 200
+        res = await session.execute(select(UserModel).where(UserModel.name == user.name))
+        assert res.scalar() is None
+        res = await session.execute(select(MemberModel).where(MemberModel.user_id == user.id))
+        assert res.scalar() is None
+
 
 class TestRefreshToken:
     @pytest.mark.asyncio