Bray Lock is a lock and weir on the River Thames in England near Bray and Dorney Reach, and is just above the M4 Bridge across the Thames. The lock is on the Buckinghamshire side of the river on the opposite bank from Bray itself and Maidenhead which are in Berkshire. Here, the county line stands roughly halfway between the lock and the opposite bank, following the course of the Thames itself. The pound lock was built by the Thames Navigation Commission relatively late, in 1845. The lock keeper's cottage is on an island between the lock and the weir.

A weir or low-head dam is a barrier across the width of a river that alters the flow characteristics of water and usually results in a change in the height of the river level. Weirs are also used to control the flow of water for outlets of lakes, ponds, and reservoirs. There are many weir designs, but commonly water flows freely over the top of the weir crest before cascading down to a lower level. There is no single definition as to what constitutes a weir.