Colchester Garrison is a major garrison located in Colchester in the county of Essex, eastern England. It has been an important military base since the Roman era. The first permanent military garrison in Colchester was established by Legio XX Valeria Victrix in AD 43, following the Roman conquest of Britain. Colchester was an important garrison town during the Napoleonic Wars and throughout the Victorian era. During the First World War, several battalions of Kitchener's Army were trained there.

Colchester is a city in northeastern Essex, England. It is the second-largest settlement in the county, with a population of 130,245 at the 2021 Census. The demonym is Colcestrian.