A slide rest is part of a metal-turning lathe, and enables the turner to precisely control the movement of the tool, by means of a screw, as it is cutting. A simple slide rest allows the tool to move along the length of the work, while the addition of a second rest at right angles to the first allows the tool to be moved in and out to the axis of rotation. The latter configuration is known as a compound slide rest. Modern lathes have the facilty of swivelling the upper slide to allow tapers to be turned.

The slide rest can be traced to the fifteenth century, and in the eighteenth century it was used on French ornamental turning lathes. The suite of gun boring mills at Woolwich Arsenal in the 1780s by the Verbruggan family also had slide rests.

Henry Maudslay never claimed he invented it, though it is highly probable he saw it when he was working at the Arsenal as a boy. In 1794, whilst he was working for Joseph Bramah, he made one, and when he had his own workshop used it extensively in the lathes he made and sold there. Coupled with the network of engineers he trained, this ensured the slide rest became widely known and copied by other lathe makers, and so diffused throughout British engineering workshops. It was Maudslay's most important achievement.

The legend that Maudslay invented the slide rest originated with James Nasmyth who wrote ambiguously about it in his Remarks on the Introduction of the Slide Principle, 1841, which later writers mis-understood and spread the story.

The first fully documented, all metal slide rest lathe was invented by Jacques de Vaucanson around 1751. It was described in the Encyclopédie a long time before Maudslay invented and perfected his version. It is likely that Maudslay was not aware of Vaucanson's work since his first versions of the slide rest had many errors which were not present in the Vaucanson lathe.