Flask is a lightweight Python web framework ideal for microservices, APIs, and small to medium applications. Gunicorn serves Flask in production as a WSGI application server, while Nginx handles SSL, static files, and load balancing. This guide deploys Flask on Ubuntu 26.04 LTS.

Tested and valid on:

  • Ubuntu 26.04 LTS

Prerequisites

  • Ubuntu 26.04 LTS with Python 3.14 and Nginx installed
  • A user with sudo privileges

Step 1 – Set Up the Project

sudo mkdir -p /var/www/myflask
sudo chown $USER:$USER /var/www/myflask
cd /var/www/myflask
python3 -m venv .venv
source .venv/bin/activate
pip install flask gunicorn

Step 2 – Create the Flask Application

cat > app.py << 'EOF'
from flask import Flask
app = Flask(__name__)

@app.route('/')
def index():
    return '
Flask on Ubuntu 26.04!
'

if __name__ == '__main__':
    app.run()
EOF

Step 3 – Create the WSGI Entry Point

cat > wsgi.py << 'EOF'
from app import app

if __name__ == '__main__':
    app.run()
EOF

Step 4 – Test Gunicorn

gunicorn --workers 3 --bind 0.0.0.0:5000 wsgi:app

Step 5 – Create a systemd Service

sudo nano /etc/systemd/system/flaskapp.service

Add:

[Unit]
Description=Gunicorn for Flask
After=network.target

[Service]
User=www-data
Group=www-data
WorkingDirectory=/var/www/myflask
Environment="PATH=/var/www/myflask/.venv/bin"
ExecStart=/var/www/myflask/.venv/bin/gunicorn --workers 3 
    --bind unix:/run/flaskapp.sock wsgi:app

[Install]
WantedBy=multi-user.target
sudo chown -R www-data:www-data /var/www/myflask
sudo systemctl start flaskapp
sudo systemctl enable flaskapp

Step 6 – Configure Nginx

sudo nano /etc/nginx/sites-available/myflask

Add:

server {
    listen 80;
    server_name example.com;
    location / {
        proxy_pass http://unix:/run/flaskapp.sock;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;
    }
}
sudo ln -s /etc/nginx/sites-available/myflask /etc/nginx/sites-enabled/
sudo nginx -t && sudo systemctl reload nginx

Step 7 – Add SSL

sudo certbot --nginx -d example.com

Conclusion

Your Flask application is now running in production on Ubuntu 26.04 LTS. Gunicorn handles concurrent requests and Nginx provides a secure, high-performance frontend. Use Flask’s application factory pattern for larger projects.