Donald Ibrahim Swann (30 September 1923 – 23 March 1994) was a British composer, musician, singer and entertainer. He was one half of Flanders and Swann, writing and performing comic songs with Michael Flanders.

Donald Swann was born in Llanelli, Carmarthenshire, Wales. His father, Herbert Alfredovich Swann, was a Russian doctor of English descent, from the expatriate community that started out as the Muscovy Company. His mother, Naguimé Sultán Swann (born Piszóva), was a Turkmen-Russian nurse from Ashgabat, now part of Turkmenistan. They were refugees from the Russian Revolution. Swann's great-grandfather, Alfred Trout Swan, a draper from Lincolnshire, emigrated to Russia in 1840 and married the daughter of the horologist to the tsars. Some time later the family added a second 'n' to their surname. His uncle Alfred wrote the first biography of Alexander Scriabin in English.

The family moved to London, where Swann attended Dulwich College Preparatory School and Westminster School. It was at the latter that he first met Michael Flanders, a fellow pupil. In July and August 1940 they staged a revue called Go To It. The pair then went their separate ways during World War II, but were later to establish a musical partnership.

In 1941 Swann was awarded an exhibition to Christ Church, Oxford, to read modern languages. He was a Quaker and pacifist. In 1942 he registered as a conscientious objector and served with the Friends' Ambulance Unit (a Quaker relief organisation) in Egypt, Palestine and Greece. After the war, Swann returned to Oxford to read Russian and Modern Greek.

When by chance Swann and Flanders met again in 1948 it led to the start of their professional partnership. They began writing songs and light opera, Swann writing the music and Flanders writing the words. Their songs were performed by artists such as Ian Wallace and Joyce Grenfell. They subsequently wrote two two-man revues, At the Drop of a Hat and At the Drop of Another Hat, which they performed all over the world until their partnership ended in 1967.

At the same time, Swann was maintaining a prolific musical output, writing the music for several operas and operettas, including a full-length version of C. S. Lewis's Perelandra, and a setting of J. R. R. Tolkien's poems from The Lord of the Rings to music in The Road Goes Ever On song cycle.

In 1953–59 Swann provided music for seven plays by Henry Reed on the BBC Third Programme, generally known as the Hilda Tablet plays after one of the fictional characters, a lady composer of avant-garde "musique concrète renforcée". Besides incidental music, Swann composed for this character an opera, "Emily Butter" and several other complete works. A lifelong friendship with Sydney Carter resulted in scores of songs, the best known being "The Youth of the Heart" which reappeared in At the Drop of A Hat, and a musical Lucy and the Hunter.

After his partnership with Flanders ended, Swann continued to give solo concerts and to write for other singers. He also formed the Swann Singers and toured with them in the 1970s. Throughout the 1980s and early 1990s, he continued performing in various combinations with singers and colleagues and as a solo artist. One such was a jazz partnership with trumpeter Digby Fairweather and vocalist Lisa Lincoln for the Swann in Jazz series of concerts and the 1994 CD.