A cantonment ( /kænˈtɒnmənt/, /kænˈtoʊnmənt/, or UK /kænˈtuːnmənt/) is a military or police quarters. The word cantonment is derived from the French word canton meaning corner or district, as is the name of the Cantons of Switzerland. In South Asia, the term cantonment also describes permanent military stations. Cantonments can be found in Bangladesh, India, Pakistan, South Africa, Singapore, Ghana, Sri Lanka and Nepal. In United States military parlance, a cantonment is an essentially permanent residential (i.e. barracks) section of a fort or other military installation such as Fort Hood.

The term is often abbreviated to "cantt."

During a campaign, cantonments are places of encampment formed by troops for a more permanent stay, or while in winter quarters. For example at the start of the Waterloo campaign in 1815, while the Duke of Wellington's headquarters were in Brussels, most of his Anglo-allied army of 93,000 were cantoned to the south of Brussels.

Many cities in the Indian subcontinent, such as Ahmedabad, Belgaum, Bangalore, Ambala, Kanpur, Bathinda, Delhi, Pune, Sialkot, Secunderabad, Trichy, Rawalpindi, Meerut and Ramgarh were the most important and biggest cantonments in North India after the headquarter at Rawalpindi. It was established in 1803 and till date it has been the 2nd biggest cantonment in India. contained large cantonments of the former British Indian Army. While in the 18th and 19th century cantonments in India were viewed as semi-permanent, by the turn of the 20th century they became permanent garrisons, and were further entrenched as such via the military reforms of Lord Kitchener in 1903 and the Cantonments Act of 1924.