The Clockmakers' Museum in London, England, is believed to be the oldest collection specifically of clocks and watches in the world. The collection belongs to and is administered by the Clockmakers’ Charity, affiliated to the Worshipful Company of Clockmakers, founded in 1631 by Royal Charter. Since 2015 it has been housed in a gallery provided by the Science Museum in South Kensington, having formerly been located in the Guildhall complex in the City of London since 1874, where it first opened to the public. Admission is free.

The formation of the collection dates back to 1814. The principal goal of the museum is to educate the public about the history of the field of clock and watchmaking (horology), principally in the City of London, and also to promote education and career possibilities in the craft of horology, which as of 2019 was placed on the HCA Red List of Endangered Crafts. The Archive of the Clockmakers is managed on its behalf by the London Metropolitan Archive and is located at Guildhall Library, where the Library collection of printed books is also held and managed.

The Clockmakers Company first established a library collection in 1814, under the control of a library committee, in which Benjamin Lewis Vulliamy soon emerged as the most prominent figure, remaining so for several decades. Early meetings were held at Vulliamy's premises in Pall Mall, London but in 1817 the Company acquired a mahogany bureau and bookcase from Gillows of Lancaster and London, to house its growing collection, and this was established in an upper room in the Kings Head Tavern in Poultry, London, where the Company had its meetings from 1802 to 1851. From 1815, the collection had expanded from books to include horological exhibits, among which an early acquisition was a set of pallets from an escapement by Alexander Cumming, bought by Vulliamy at auction, and which are still on display, on the Gillows bookcase.

With the deaths of BL Vulliamy and George Atkins, Clerk to the Company, in the 1850s, the collection lost its key advocates and supporters, but the fortunes of the museum were reversed with the construction of a new building for Guildhall Library in the early 1870s. At the invitation of the Guildhall authorities, the Clockmakers’ Museum was moved there and opened to the public from 1873. A first catalogue was written by William Henry Overall in 1875. In 1891, The Rev Harry Leonard Nelthropp, a key supporter of the museum, persuaded the Company to acquire one of the most important items in the modern collection, John Harrison’s fifth marine timekeeper, H5. In 1894, Nelthropp donated his entire personal collection of watches, clocks, sundials, seals and related ephemera to the Museum. Charles Welch produced a new catalogue in 1902.

In 1936, the Clockmakers asked the noted engineer and horologist Granville Hugh Baillie to create a new catalogue. Baillie rearranged the museum between mid-1937 and mid-1938. During the Second World War the collection was dismantled and stored off-site under the guidance of Guildhall Librarian James Lungley Douthwaite. Baillie produced a guide in 1939 and updated the catalogue in 1949.

The museum moved to the new Guildhall Library in 1976, and, in anticipation, Cecil Clutton and George Daniels produced a new catalogue of the clock and watch collection, while John Bromley, a Guildhall Librarian, produced a new catalogue of the Library collection.

Under Cedric Jagger as Assistant Curator from 1974, and then as Keeper from 1980, the Museum underwent significant reorganization and improvement at Guildhall. Jagger was succeeded as Keeper by Sir George White in 1988, who served for thirty years through to 2018, in which time the museum and archive collection was again expanded. The major acquisitions in the late twentieth and early twenty-first century were the Hurle-Bath and Hurle-Bradley watch collections, and the purchase of a significant cache of original John Harrison manuscript documents. With a major bequest by noted collector and Past-Master of the Company Reginald Gowan Beloe TD, the funds were available for a major rebuild of the museum, which reopened with a new and enlarged display organized by White at Guildhall Library in 2001. When its lease finally expired at Guildhall, White was instrumental in securing the offer by Ian Blatchford of a newly designed gallery at the Science Museum, which it now occupies under a thirty-year lease. The collection was moved over the course of 2014–15, and the new gallery was opened by the Princess Royal on 22 October 2015. The new gallery is more than twice the size of the earlier gallery at Guildhall. Visitor numbers in the decade prior to 2014 were of the order of 13,000 per annum, but since the move to the Science Museum numbers have expanded significantly, in view of the more than 3 million visitors to the London Science Museum site each year.

The move of the Clockmakers Museum to the Science Museum formed part of the updating and improvement of the Science Museum second floor galleries, where it adjoins the Mathematics Gallery (designed by Zaha Hadid Architects, opened 2016) and Science City: 1500–1800 (designed by Gitta Gschwendtner, opened 2019).