Calshot Castle forms part of Henry VIIIs chain of artillery fortifications along the south coast of England. Built in 1539, it defended the narrow entrance to Southampton Water and the port of Southampton against threat of invasion from French and Spanish forces.

During the 20th century it was repurposed a military aviation hub. As Royal Navy Air Station Calshot it was used as a base for seaplanes and later hosted meetings of the Schneider Trophy air race. It is now open to the public and managed by English Heritage.