The Old Operating Theatre Museum and Herb Garret is a museum of surgical history and one of the oldest surviving operating theatres. It is located in the garret of St Thomas’s Church, Southwark, in London, on the original site of St Thomas’ Hospital.

There is little information about operating theatres at Old St Thomas from its foundation till the 18th century. The church that contains the Old Operating Theatre Museum was built at the end of the 17th century, when the hospital and church were largely rebuilt by Sir Robert Clayton, president of the hospital and a former Lord Mayor of the City of London. He employed Thomas Cartwright as architect. (Cartwright was master mason to Christopher Wren at St Mary-Le-Bow). The new church was fitted out with a large garret constructed in the ‘aisled-barn’ tradition. Very little information exists about the Garret except that it was fitted with wooden storage racks, and was described as “the herb garret” in 1821. Dried heads of opium plants were found in the rafters. It is likely that the garret was used by the hospital’s resident apothecary to store and cure medicinal herbs.

In 1822 part of the herb garret was converted into a purpose-built operating theatre. This strange situation resulted from the fact that the female surgical ward abutted the garret. Previously operations took place on the ward. Windows were also provided for the Garret at the same time, suggesting that its function changed from storage to a working environment. It may have been used as a recovery ward.

In 1859, Florence Nightingale became involved with St Thomas’s, setting up on this site her famous nursing school. It was on her advice that the Hospital agreed to move to a new site when the Charing Cross Railway Company offered to buy the hospital’s land. In 1862, the hospital began the move to its present site at Lambeth and the operating theatre was closed. The theatre lay undiscovered until 1957.