The Waag is a 15th-century building on Nieuwmarkt square in Amsterdam. It was originally a city gate and part of the walls of Amsterdam. The building has also served as a guildhall, museum, fire station and anatomical theatre, among other things.
The Waag is the oldest remaining non-religious building in Amsterdam. The building was listed as a national monument in 1970.
The Waag is depicted in Rembrandt's 1632 painting The Anatomy Lesson of Dr. Nicolaes Tulp. The surgeons' guild commissioned this painting for their guildhall in the Waag.