John Slezer (before 1650 – 1717) was a Dutch- or German-born military engineer and artist. He arrived in the Kingdom of Scotland in 1669,[1] and was appointed Surveyor of his Majesties Stores and Magazines, which involved compiling detailed surveys of the country's fortifications. He is best known for his Theatrum Scotiae, a series of engravings of views of castles, towns, and other landmarks he encountered whilst travelling throughout Scotland in his capacity as Captain of the Artillery Company. He was imprisoned in 1688 as a supporter of King James VII, following the latter's deposition in favour of William and Mary, but was released the following year. He published the first volume of Theatrum Scotiae in 1693, but sales were poor, and Slezer was forced to seek sanctuary at Holyrood Abbey to avoid debtors' prison.