A tide mill is a water mill driven by tidal rise and fall. A dam with a sluice is created across a suitable tidal inlet, or a section of river estuary is made into a reservoir. As the tide comes in, it enters the mill pond through a one-way gate, and this gate closes automatically when the tide begins to fall. When the tide is low enough, the stored water can be released to turn a water wheel.

Tide mills are usually situated in river estuaries, away from the effects of waves but close enough to the sea to have a reasonable tidal range. Cultures that built such mills have existed since the Middle Ages, and some may date back to the Roman period.

A modern version of a tide mill is the electricity-generating tidal barrage.

Possibly the earliest tide mill in the Roman world was located in London on the River Fleet, dating to Roman times.

Since the late 20th century, a number of new archaeological finds have consecutively pushed back the date of the earliest tide mills, all of which were discovered on the Irish coast: A 6th-century vertical-wheeled tide mill was located at Killoteran near Waterford. A twin-flume, horizontal-wheeled tide mill, dating to c. 630, was excavated on Little Island in Cork. Alongside it, another tide mill was found that was powered by a vertical undershot wheel. The Nendrum Monastery mill from 787 was situated on an island in Strangford Lough in Northern Ireland. Its millstones are 830mm in diameter and the horizontal wheel is estimated to have developed 7–8 horsepower (5.2–6.0 kW) at its peak. Remains of an earlier mill dated at 619 were also found at the site.

In England, an exceptionally well preserved tidal mill, dated by dendrochronology to the late 7th century (691-692 AD) was excavated in the Ebbsfleet Valley (a minor tributary of the River Thames) in Kent during construction of the Ebbsfleet International Station, on the High Speed 1 railway line The earliest recorded tide mills in England are listed in the Domesday Book (1086). Eight mills are recorded on the River Lea (the site at Three Mills remains, with Grade I listed buildings and a small museum), as well as a mill in Dover harbour. By the 18th century, there were about 76 tide mills in London, including two on London Bridge.

Tide mills in southern Iraq, positioned at the mouth of the Tigris-Euphrates river delta in Basra, were described in 960.

Woodbridge Tide Mill, an excellent example, survives at Woodbridge, Suffolk, England. This mill, dating from 1170 and reconstructed in 1792, has been preserved and is open to the public. It was further restored in 2010 and re-opened in 2011 in full working order. It is the second working tide mill in the United Kingdom that is regularly producing flour. Carew Castle in Wales also has an intact tide mill, but it is not operating. The first tide mill to be restored to working order is Eling Tide Mill in Eling, Hampshire. Another example, now extant only in historic documents, is the mill in the hamlet of Tide Mills, East Sussex. Traces of a tide mill may be seen at Fife Ness, revealed through an archaeological survey