The Flint Subdivision is a railway line in the state of Michigan.

At Port Huron, on the shores on Lake Huron, it connects with the Strathroy Subdivision which runs through the St. Clair Tunnel into Ontario.

Historically, the line was part of the Grand Trunk Western Railroad mainline between Chicago and Toronto.

Amtrak's Blue Water uses the line between Battle Creek and Port Huron.

Freight yards on or near the line are located in Port Huron, Flint, Durand, Lansing, and Battle Creek.