You try to start a container and Docker complains:

Error response from daemon: network mynetwork not found

The container is referencing a network that doesn’t exist on the Docker host.

What causes this

Docker containers can be attached to user-defined networks for inter-container communication. When you reference a network by name — either in a docker run command or a docker-compose.yml — Docker looks it up by that exact name. If it doesn’t exist, you get this error.

Common causes:

• You’re running a container that expects a network created by another Compose project
• The network was manually deleted or cleaned up with docker system prune
• There’s a typo in the network name
• You ran docker compose down which removes project networks, then tried to start a standalone container that depended on one
• You’re on a different machine or Docker context where the network was never created

Fix 1: Create the network manually

If you know the network name, just create it:

docker network create mynetwork

Then run your container:

docker run --network mynetwork my-image

You can specify the driver if needed (default is bridge):

docker network create --driver bridge mynetwork

Fix 2: List existing networks to find the right name

Maybe the network exists but with a different name. Docker Compose prefixes network names with the project name:

docker network ls

Output might look like:

NETWORK ID     NAME                    DRIVER
abc123         bridge                  bridge
def456         myproject_mynet         bridge

If you see myproject_mynet instead of mynet, use the full name or set an explicit name in your Compose file.

Fix 3: Define the network in Docker Compose

When using Docker Compose, networks are auto-created when you run docker compose up. Define them explicitly:

services:
  web:
    image: nginx
    networks:
      - mynet
  api:
    image: node:18
    networks:
      - mynet

networks:
  mynet:
    driver: bridge

If you need the network to have a specific name (without the project prefix), set it explicitly:

networks:
  mynet:
    name: mynetwork
    driver: bridge

Fix 4: Use an external network

If multiple Compose projects need to share a network, declare it as external:

networks:
  shared:
    external: true
    name: mynetwork

This tells Compose “don’t create this network — it already exists.” You must create it manually first with docker network create mynetwork.

Fix 5: Clean up and recreate

If things are in a messy state, tear everything down and start fresh:

docker compose down
docker network prune
docker compose up -d

The network prune command removes all unused networks. Then docker compose up recreates the ones defined in your Compose file.

Related resources

• Docker cheat sheet
• Docker complete guide

How to prevent it

• Use Docker Compose to manage networks — it handles creation and cleanup automatically
• If you share networks across projects, use external: true and document the setup step
• Be careful with docker system prune — it removes unused networks along with everything else
• Use explicit name fields in Compose network definitions to avoid confusion with auto-prefixed names