The Royal Munster Fusiliers was a line infantry regiment of the British Army from 1881 to 1922. It traced its origins to the East India Company's Bengal European Regiment raised in 1652, which later became the 101st Regiment of Foot (Royal Bengal Fusiliers). The Royal Munster Fusiliers were formed in 1881 by the merger of the 101st Regiment of Foot and the 104th Regiment of Foot (Bengal Fusiliers). One of eight Irish regiments raised largely in Ireland, it had its home depot in Tralee and served as the county regiment for Cork, Clare, Limerick and Kerry. At its formation the regiment comprised two regular and two militia battalions.

The Royal Munster Fusiliers served in India before the regiment fought in the Second Boer War. Prior to the First World War, the regiment's three militia battalions were converted into reserve battalions, and a further six battalions were added to the regiment's establishment during the war. The regiment fought with distinction throughout the Great War and won three Victoria Crosses by the conflict's conclusion in 1918. Following establishment of the independent Irish Free State in 1922, the five regiments that had their traditional recruiting grounds in the counties of the new state were disbanded and the Royal Munster Fusiliers ceased to be as a regiment on 31 July 1922.

Before the regiment was reformed as part of a reorganization of the British Army in 1881, the Royal Munster Fusilier's historic background went back as far as 1652 with the formation of the Bengal European Regiment by the Honourable East India Company. This regiment would eventually become the 101st Regiment of Foot (Royal Bengal Fusiliers), or the 1st Bengal European Fusiliers. The East India Company formed the 104th Regiment of Foot (Bengal Fusiliers), or 2nd Bengal European Fusiliers, from this regiment in 1765. Both regiments, which were composed exclusively of white soldiers, not Indian sepoys, played pivotal roles in the British conquest of India throughout the 18th and 19th centuries.

As well as the Royal Munster Fusilier's origins as part of the East India Company, the regiment's reserve battalions also traced their lineage to the Militia of Munster (namely the South Cork Light Infantry Militia, the Kerry Militia and the Royal Limerick County Militia, which became the 3rd, 4th and 5th Battalions, respectively). While both the fusilier regiments had originated and served as "European" regiments of the East India Company, they were transferred to the British Army in 1861 when the British Crown took control of the company's private army after the Indian Mutiny of 1857.

The second half of the 19th Century saw the beginning of widespread reforms in the British Army which would eventually result in the formation of the Royal Munster Fusiliers. The first of these reforms saw the localisation of recruiting districts in Britain and Ireland between 1873 and 1874 under the Cardwell Reforms. Five of the historic East India Company's European infantry battalions were given Irish territorial titles under the Childers Reforms of 1881. The former Bengal Fusilier regiments were merged into a single regiment to become the 1st Battalion, Royal Munster Fusiliers and the 2nd Battalion, Royal Munster Fusiliers, while the 3rd, 4th and 5th Royal Munster Fusilier battalions were the militia units. The Reforms linked regiments to recruiting areas – which in case of the Royal Munster Fusiliers were the counties of Clare, Cork, Kerry, and Limerick. Militarily, the whole of Ireland was administered as a separate command with Command Headquarters at Parkgate (Phoenix Park) Dublin, directly under the War Office in London. The regimental depot was located at Ballymullen Barracks, Tralee, County Kerry.

Following the outbreak of the Second Boer War in South Africa in October 1899, a number of regiments from areas containing large centres of population formed additional regular battalions. The Royal Munster Fusiliers were announced to be among those regiments set to form 3rd and 4th regular battalions in February 1900, but they do not appear to have done so. The 1st Royal Munster Fusiliers embarked for South Africa in 1899, and would serve there throughout the entire Second Boer War. Initially, the battalion took part in Lord Robert's advance into the Orange Free State. Following this, the battalion was attached to the 20th Brigade and fought at the Battle of Belmont. With the beginning of the war's guerrilla warfare phase, the battalion took part in numerous pacification campaigns against the Boers in Pretoria and Western Transvaal. The 3rd (Militia) Battalion, Royal Munster Fusiliers, formerly the South Cork Light Infantry, was embodied in early December 1899, and 435 officers and men embarked the SS Sumatra for South Africa on 23 February 1900. The 2nd Battalion, Royal Munster Fusiliers, arrived in South Africa from India in December 1901 and served during the closing stages of the campaign, garrisoning blockhouses in the northeast of the Orange River Colony.

Following the end of the war in 1902 the 1st Royal Munster Fusiliers were sent to India. More than 520 officers and men left Cape Town on the SS Lake Manitoba in September 1902, arriving at Bombay the following month and were then stationed at Multan in Punjab. They would later take part in actions against the tribes of the North-West Frontier in 1908. The 2nd Royal Munster Fusiliers left South Africa soon after their sister battalion, and 450 officers and men returned to Cork Harbour on the SS Orient in early November 1902.

Prior to the First World War, the Royal Munster Fusiliers were an established strength of two regular service and three reserve battalions. With the outbreak of war in August 1914, the need for further divisions resulted in the creation of a New Army made up of volunteers who would serve for the duration of the war. This rapid expansion of the British Army would significantly increase the size of the Royal Munster Fusiliers who between their regular, reserve and volunteer battalions would have a combined strength of 11 raised battalions throughout the war.