The Royal College of Nursing (RCN) is a registered trade union and professional body in the United Kingdom for those in the profession of nursing. It was founded in 1916 as the College of Nursing, receiving its royal charter in 1928. Queen Elizabeth II was the patron until her death in 2022, King Charles III continued the royal connection and became patron in 2024. The majority of members are registered nurses; however student nurses and healthcare assistants are also members. There is also a category of membership, at a reduced cost, for retired people.

The RCN describes its mission as representing nurses and nursing, promoting excellence in practice and shaping health policies. It has a network of stewards, safety representatives and union learning representatives as well as advice services for members. Services include a main library in London, and regional libraries. The RCN Institute provides courses for nurses.

The College of Nursing Ltd was founded on 27 March 1916, with 34 members, as a professional organisation for trained nurses. On a proposal from Dame Sarah Swift (then matron of Guy's Hospital ) and Arthur Stanley, chairman of the Joint War Organisation, developed with Rachael Cox-Davies (matron of the Royal Free Hospital) and Alicia Lloyd-Still (matron of St. Thomas Hospital ) the College was founded with articles of association. The objectives of the College were 1) to promote better education and training of nurses, 2) to promote uniformity of curriculum, 3) to recognise approved nursing schools, 4) to make and maintain a register of persons who had certificates of proficiency in nursing and 5) promote bills in parliament in support of the interests of the nursing profession. Eleven matrons signed the founding articles of Association, one of whom was Margaret Elwyn Sparshott. It attempted amalgamation with the Royal British Nurses' Association, but this was frustrated, largely by the efforts of Ethel Gordon Fenwick. In March 1917 the college had 2,553 members and, by 1919, 13,047, a great deal more than the RBNA. It had most of the nursing places on the General Nursing Council when it was first established, and by 1925 it had about 24,000 members. Membership was restricted to registered general nurses. The college initially excluded male nurses, and those on the mental, mental subnormality, fever and children's nurses' registers from membership. Annie Warren Gill was one of the founders of the Scottish board of the College of Nursing which held its first meeting on 1 November 1916 in Edinburgh. She was instrumental in setting up local branches in Scotland to increase membership. Gill also proposed in 1922 that married members be considered part of the College, having realised that there would be a nursing shortage following World War 1.

A royal charter was granted in 1928.The organisation became the College of Nursing and Frances Goodall its Assistant General Secretary. The college pushed for registered nurses to be given precedence, and to be in charge. In 1935 Frances Goodall became General Secretary and the Trades Union Congress promoted a Parliamentary bill to secure a 48-hour working week for all hospital employees. The college opposed this and was accused by the TUC of being "an organisation of voluntary snobs". In 1939 the college's name was changed to “the Royal College of Nursing”. The Ministry of Health guaranteed a salary of £40 to nursing students in training in 1941, about double what voluntary hospitals were paying before the war. The College said that this was too high. In 1943 the College held nine seats to represent 'employees' on the Nurses Salaries Committee chaired by Lord Rushcliffe which published two reports in 1943. In the 1940s the College joined efforts by the Equal Pay Campaign Committee to secure equal pay for public sector employees, particularly women civil servants, teachers and nurses, which in 1955 was agreed by government to be implemented in stages. In 1963, active RCN member Grace Margery Westbrook became the first practising nurse to be elected Chair of the Staff Side Committee, Nurses and Midwives Whitley Council 1963-1969; her RCN activities had included being elected Council member representing Southern England in 1959.

Since 1977 the RCN has been registered as a trade union.

In 2018, after a pay agreement was not clearly explained to the membership, the Chief Executive and General Secretary Janet Davies resigned and Dame Donna Kinnair was appointed in an acting capacity. She was confirmed in the role in April 2019. A motion of no confidence in the RCN Council was called shortly afterwards and passed in September 2018 with 78% of votes, but on a turnout when only 3.7% of the membership voted. As well as the Chief Executive and General Secretary, the Director of Member Relations had previously resigned. Twelve of the 17 council members resigned, 10 of them standing for re-election in the subsequent election.

In 2019, the RCN's first strike – limited to Northern Ireland, over staffing and pay issues – took place.

In May 2019, the Royal College of Nursing voted to back the “decriminalisation” of prostitution.