Full example

Here is a full working example with JWT authentication to help get you started.

SQLAlchemy

import databases
import sqlalchemy
from fastapi import FastAPI
from fastapi_users import BaseUser, FastAPIUsers
from fastapi_users.authentication import JWTAuthentication
from fastapi_users.db import SQLAlchemyBaseUserTable, SQLAlchemyUserDatabase
from sqlalchemy.ext.declarative import DeclarativeMeta, declarative_base

DATABASE_URL = "sqlite:///./test.db"
SECRET = "SECRET"


database = databases.Database(DATABASE_URL)

Base: DeclarativeMeta = declarative_base()


class UserTable(Base, SQLAlchemyBaseUserTable):
    pass


engine = sqlalchemy.create_engine(
    DATABASE_URL, connect_args={"check_same_thread": False}
)

Base.metadata.create_all(engine)

users = UserTable.__table__
user_db = SQLAlchemyUserDatabase(database, users)


class User(BaseUser):
    pass


auth = JWTAuthentication(secret=SECRET, lifetime_seconds=3600)

app = FastAPI()
fastapi_users = FastAPIUsers(user_db, auth, User, SECRET)
app.include_router(fastapi_users.router, prefix="/users", tags=["users"])


@fastapi_users.on_after_register()
def on_after_register(user: User):
    print(f"User {user.id} has registered.")


@fastapi_users.on_after_forgot_password()
def on_after_forgot_password(user: User, token: str):
    print(f"User {user.id} has forgot their password. Reset token: {token}")


@app.on_event("startup")
async def startup():
    await database.connect()


@app.on_event("shutdown")
async def shutdown():
    await database.disconnect()

MongoDB

import motor.motor_asyncio
from fastapi import FastAPI
from fastapi_users import BaseUser, FastAPIUsers
from fastapi_users.authentication import JWTAuthentication
from fastapi_users.db import MongoDBUserDatabase

DATABASE_URL = "mongodb://localhost:27017"
SECRET = "SECRET"


client = motor.motor_asyncio.AsyncIOMotorClient(DATABASE_URL)
db = client["database_name"]
collection = db["users"]


user_db = MongoDBUserDatabase(collection)


class User(BaseUser):
    pass


auth = JWTAuthentication(secret=SECRET, lifetime_seconds=3600)

app = FastAPI()
fastapi_users = FastAPIUsers(user_db, auth, User, SECRET)
app.include_router(fastapi_users.router, prefix="/users", tags=["users"])


@fastapi_users.on_after_register()
def on_after_register(user: User):
    print(f"User {user.id} has registered.")


@fastapi_users.on_after_forgot_password()
def on_after_forgot_password(user: User, token: str):
    print(f"User {user.id} has forgot their password. Reset token: {token}")

What now?

You're ready to go! Be sure to check the Usage section to understand how yo work with FastAPI Users.