Stedelijk Gymnasium Leiden is a gymnasium in the Netherlands. Located in Leiden, it is one of the oldest schools in the Netherlands. Its history dates back to the Middle Ages. The Stedelijk Gymnasium Leiden is the biggest gymnasium-only school in the Netherlands, with over 1,800 pupils.

Leiden is a city and municipality in the province of South Holland, Netherlands. The municipality of Leiden has a population of 127,046, but the city forms one densely connected agglomeration with its suburbs Oegstgeest, Leiderdorp, Voorschoten and Zoeterwoude with 215,602 inhabitants. The Netherlands Central Bureau of Statistics (CBS) further includes Katwijk in the agglomeration which makes the total population of the Leiden urban agglomeration 282,207 and in the larger Leiden urban area also Teylingen, Noordwijk, and Noordwijkerhout are included with in total 365,913 inhabitants. Leiden is located on the Oude Rijn, at a distance of some 20 km (12 mi) from The Hague to its south and some 40 km (25 mi) from Amsterdam to its north. The recreational area of the Kaag Lakes (Kagerplassen) lies just to the northeast of Leiden.