The Kent Militia was an auxiliary military force in the county of Kent in South East England. From their formal organisation as Trained Bands in 1558 until their final service as the Special Reserve, the Militia regiments of the county served in home defence in all of Britain's major wars. They also saw active service during the Second Boer War, and trained thousands of reinforcements during World War I. After a shadowy postwar existence they were formally disbanded in 1953.

The English militia was descended from the Anglo-Saxon Fyrd, the military force raised from the freemen of the shires under command of their Sheriff. The universal obligation to serve continued under the Norman and Plantagenet kings and was reorganised under the Assizes of Arms of 1181 and 1252, and again by the Statute of Winchester of 1285. The men were arrayed by the Hundreds into which each county was divided. Under this statute 'Commissioners of Array' would levy the required number of men from each shire. The usual shire contingent was 1000 infantry commanded by a millenar, divided into companies of 100 commanded by centenars or ductores, and subdivided into platoons of 20 led by vintenars. The coastal towns of Kent forming part of the Cinque Ports also had a legal obligation to supply ships, seamen and marines for the Royal Navy.

Under the later Tudors the legal basis of the militia was updated by two acts of 1557 covering musters (4 & 5 Ph. & M. c. 3) and the maintenance of horses and armour (4 & 5 Ph. & M. c. 2), which placed the county militia under a Lord Lieutenant appointed by the monarch, assisted by the Deputy Lieutenants and Justices of the Peace. The entry into force of these Acts in 1558 is seen as the starting date for the organised county militia in England.

Although the militia obligation was universal, it was clearly impractical to train and equip every able-bodied man, so after 1572 the practice was to select a proportion of men for the Trained Bands, who were mustered for regular drills. When war broke out with Spain training and equipping the militia became a priority. From 1583 counties were organised into groups for training purposes, with emphasis on the invasion-threatened 'maritime' counties including Kent. In 1584, Kent had 2500 trained men, of which 1000 were equipped with firearms, 500 with bows and 1000 were 'corslets' (armoured pikemen).

The Armada Crisis in 1588 led to the mustering of the trained bands in April and they were called out on 23 July as the Armada approached. Kent produced 7124, of whom 4166 were untrained. Kent was threatened on its southern, eastern and northern coasts and its force was divided into eastern and western divisions at Maidstone and Canterbury respectively. Two thousand of the Kent trained men were sent to join the main Royal army at St James's Palace in London, and 4000 foot and 725 horse were to be sent into the neighbouring county of Sussex if the Spanish landed there. But the Armada was defeated at sea and was unable to land any troops: the trained bands were stood down shortly afterwards.

With the passing of the threat of invasion, the trained bands declined in the early 17th Century. Later, King Charles I attempted to reform them into a national force or 'Perfect Militia' answering to the king rather than local control. In 1638 the Kent regiments were organised by 'lathes' (the ancient groups of Hundreds into which Kent was subdivided): Aylesford (Rochester, Maidstone and Tonbridge areas); St Augustine Lathe (Canterbury, Sandwich and Dover areas); Scray Lathe (Ashford area); Shepway Lathe (Folkestone, Hythe and New Romney areas) and Sutton-at-Hone Lathe (Dartford and Sevenoaks areas), together with one company from the City of Canterbury. These totalled 2910 musketeers, 1757 corslets, and 293 horse.

The trained bands including the Kent contingent were called out in both 1639 and 1640 for the Bishops' Wars. In 1639 the county was ordered to select 1200 men for Sir Thomas Morton's Regiment of Foot in the Marquess of Hamilton's army, which was to make an amphibious landing in Scotland. But the best men were kept for coastal defence and most of those who actually went were untrained and badly equipped hired or 'pressed' substitutes, the men and arms described as 'utterly unserviceable'. Morton's Regiment took part in the abortive expedition, suffering serious casualties from an outbreak of smallpox before the army was dispersed to its homes. Kent's quota in 1640 was another 700, not including the Cinque Ports' 300, to be sent by sea to join the army assembling on the Scottish border. Kent however was notably uncooperative and the numbers had to be made up with pressed men.

Control of the trained bands was one of the major points of dispute between Charles I and Parliament that led to the English Civil War. However, with a few exceptions neither side made much use of the trained bands during the war beyond securing the county armouries for their own full-time troops, many of whom were recruited from the trained band ranks. However, the Kent Trained Bands were often called out and as the war dragged on the county organised Auxiliary Trained Bands to allow rotation of units on duty. They also raised units of volunteers for service outside the county. Each of the five lathes organised an auxiliary regiment and a regiment of horse: