ModuleNotFoundError: No module named 'multipart'

How to fix ModuleNotFoundError: No module named 'multipart'

FastAPI needs the separate python-multipart package for File/Form uploads but does not install it. Run python -m pip install python-multipart and add it to requirements.txt. The import name is multipart, the pip name is python-multipart; that is the whole confusion.

The exact error

ModuleNotFoundError: No module named 'multipart'

Fix it

1. python -m pip install python-multipart

Expected: Successfully installed python-multipart

1. python -c "import multipart"

Expected: no error

1. Add python-multipart to requirements.txt and redeploy.

Expected: uploads work in the deployed env too

When this applies

FastAPI/Starlette app using UploadFile, File(...) or Form(...) raises No module named 'multipart'

When this does NOT apply

you are not doing file uploads (then you do not need it at all)

Versions

FastAPI file uploads / Form data

Why it happens

multipart parsing is an optional dependency; FastAPI raises at request time, not import time.

Edge cases

python-multipart 0.0.18+ changed some internals; if an old pin breaks, unpin it.