The Underfall Yard is a historic boatyard on Spike Island serving Bristol Harbour, the harbour in the city of Bristol, England. Underfall Yard was commonly referred to as "The Underfalls" and takes its name from the underfall sluices. The original construction (designed by William Jessop) was in the early 19th century with revisions by Isambard Kingdom Brunel in the 1830s. Following restoration in the 1990s, this Victorian work yard is now a Scheduled Monument that includes several listed buildings. The harbour and its equipment are still actively maintained, and host a cooperative of boat builders.

The octagonal brick and terracotta chimney of the engine house dates from 1888, and is grade II* listed, as is the hydraulic engine house itself. It replaced the original pumping house which is now The Pump House public house. It is built of red brick with a slate roof and originally contained two steam engines. These were replaced in 1907 by the current electric machines from Fullerton, Hodgart and Barclay of Paisley. It powers the docks hydraulic system of cranes, bridges and locks.

The original slipway was built by John Ward Girdlestone in 1890 which had replaced a predecessor built in the 1850s by boatbuilders Ross and Sage. It used a system in which the ship is floated onto the cradle and secured. The cradle is then drawn out of the water with a steam-driven winch. The device was a low-cost alternative to dry docks for maintenance and repair work. This became known as the Patent slipway or 'Heave-up Slip' and was patented in 1819 by shipbuilder Thomas Morton of Leith in Scotland.