The Royal Berkshire Militia was a militia regiment in the United Kingdom from 1759 to 1881, when it was amalgamated into The Princess Charlotte of Wales's (Berkshire Regiment).
A Berkshire Militia was embodied at Reading during the English Civil War, but with no formal connection to the later regiment.
The regiment was organised in 1759, as the Berkshire Militia, and designated "Royal" the following year. It was embodied in 1778, at which time it was ranked the 34th regiment of militia, and remained active for five years. It was regularly re-ranked through its embodiment, becoming the 11th in 1779, 25th in 1780, 29th in 1781, and 20th in 1782.
It was embodied again in 1793 for the French Revolutionary Wars, ranked as the 30th. With the resumption of hostilities in 1803, it was embodied as the 37th, and disembodied in 1816 following the peace.
In 1833, it was ranked as the 7th. It saw service during the Crimean War, being embodied in 1855 and volunteering for garrison service in the Mediterranean, being embodied again in late 1857 and finally disembodied in 1858.
In 1881, under the Childers Reforms, the regiment was transferred into The Princess Charlotte of Wales's (Berkshire Regiment) as the 3rd Battalion. This was embodied during the South African War in 1900. It was disembodied in mid-1901.
During the Haldane Reforms in 1908 the battalion was transferred to the Special Reserve, and was embodied on mobilisation in 1914 for the First World War. As with all Special Reserve battalions, it served as a regimental depot, and was disembodied following the end of hostilities in 1919, with personnel transferred to the 2nd Battalion. The battalion nominally remained in existence throughout the Second World War, but was never activated, and was finally disbanded in 1953.