A Boat Passing a Lock is an 1826 landscape painting by the British artist John Constable.

It portrays a scene at Flatford Lock on the River Stour in Suffolk, an area now known as "Constable Country".

It borrows from the composition of his earlier painting The Lock, but switches from a portrait to a landscape format and alters some of the action.

[1] In 1829 when Constable was elected to full membership of the Royal Academy of Arts he submitted this as his diploma work.

[2] By then it was in the ownership of the bookseller James Carpenter, with Constable taking it back in exchange for the promise of another painting Helmingham Dell.