Hornsby Maintenance Depot is a Sydney Trains train depot in the northern Sydney suburb of Asquith.
The depot opened in 1928 and was one of four electric train depots built under the Bradfield electrification plan, the other depots being at Mortdale, Flemington and Punchbowl (later closed).
The depot features nine roads under the main shed (numbered 1-9), five outdoor roads (numbered 11-15), two of which (11 and 12) are elevated, a train washing facility (16 road) and several short outdoor storage sidings. The depot is responsible for the stabling and maintenance of all trains on the Northern, North Shore, and Western lines (collectively known as Sector 3). Some Sydney Trains K sets, as well as an allocation of T sets are maintained at Hornsby.