The York and Lancaster Regiment was a line infantry regiment of the British Army that existed from 1881 until 1968. The regiment was created in the Childers Reforms of 1881 by the amalgamation of the 65th (2nd Yorkshire, North Riding) Regiment of Foot and the 84th (York and Lancaster) Regiment of Foot. The regiment saw service in many small conflicts and both World War I and World War II until 1968, when the regiment chose to be disbanded rather than amalgamated with another regiment, one of only two infantry regiments in the British Army to do so, with the other being the Cameronians (Scottish Rifles).

The regiment was formed on 1 July 1881 through the amalgamation of two regiments of foot and a militia regiment:

Under the original scheme of amalgamation announced in March 1881 the title of the new regiment was to be The Hallamshire Regiment. This reflected the fact that the regimental district included an area of West Riding of Yorkshire known as Hallamshire. The proposed title was unpopular with the amalgamating units, who sought a more "suitable title... which at the same time would identify the regiment with the county (Yorkshire), which the word 'Hallamshire' entirely fails to do." Four different titles were proposed, and following a vote of the officers of all four battalions, the title York and Lancaster Regiment was chosen. The regiment inherited the title "York and Lancaster" from the 84th Foot to which had been awarded in 1809. The 84th was one of the few Regiments of Foot lacking a county designation and the title was given in recognition of the fact that the unit had been raised in York in 1793, with a second battalion in Preston, Lancashire in 1808.

The 1st battalion of the new regiment had spent 11 years in India (as the 65th Reg) 1871–1882. They were moved to Aden to be held in reserve for the Egyptian Campaign. After 18 months, they shipped on the Serapis to Trinkitat, Sudan, arriving 28 February 1884. The next day they came under gun fire and made a bayonet charge, capturing two Krupp guns. Later that day seven were killed and 35 wounded at the Battle of El Teb. The 1st battalion was reported as 421 strong when at Souakim, 14 March, before losing 32 killed and 25 wounded. They embarked on the troopship HMS Jumna on 29 March, arriving at Dover on 22 April 1884.

The 1st battalion embarked for South Africa as part of the reinforcements for the Second Boer War in late 1899. It took part in the Relief of Ladysmith.

Following the end of the war in South Africa in 1902, the 1st battalion was sent to British India, where it replaced the 2nd battalion in Mhow. The 2nd battalion returned home, for the first time since 1883.

In 1908, the Volunteers and Militia were reorganised nationally, with the former becoming the Territorial Force and the latter the Special Reserve; the regiment now had one Reserve and two Territorial battalions.

In total, 22 battalions of the regiment served during the Great War, losing 8,814 officers and men killed in action.