Weymouth Harbour sits at the mouth of the River Wey, where the chalk stream completes its roughly 12-kilometre journey from Upwey and empties into the southwest corner of Weymouth Bay on Dorset's English Channel coast.

Entered between two stone piers, the harbour follows the river's path through the town, giving it a long, narrow, and unusually deep character. The harbour serves as both a working port and a busy leisure destination.

A Ro-Ro cross-channel ferry terminal operates from its north side, while visiting leisure craft can take up pontoon berths along the historic quays.

The outer harbour offers good protection in most conditions, though swell can penetrate in strong easterly and north-easterly winds. A lifting town bridge separates the outer harbour from the inner marina channel beyond.