Events from the year 1821 in Scotland.

• 15 January – Sumburgh Head Lighthouse in Shetland, designed by Robert Stevenson, is first illuminated.
• 28 April – foundation stone for the Melville Monument in St Andrew Square, Edinburgh, is laid.^[1]
• 18 July – thief David Haggart is hanged in Edinburgh, aged 20, for the murder of a Dumfries tolbooth keeper in 1820, leaving an autobiography, The life of David Haggart, and phrenologist George Combe's Phrenological observations on the cerebral development of David Haggart.
• 14 August – Trinity Chain Pier opens at Trinity, Edinburgh.
• 16 October – the School of Arts of Edinburgh, a predecessor of Heriot-Watt University, is established by Leonard Horner for the education of working men.^[2][3]
• The Royal Scottish Society of Arts is founded as The Society for the Encouragement of the Useful Arts in Scotland by David Brewster.
• The publisher T&T Clark is established in Edinburgh by Thomas Clark.
• William Hooker (botanist) publishes Flora Scotica; or, A description of Scottish plants.
• Robert Owen's Report to the County of Lanark, of a plan for relieving public distress and removing discontent is published in Glasgow.

• 10 March – Màiri Mhòr nan Òran, Gaelic poet (died 1898)
• 15 March – William Milligan, theologian (died 1893)
• 11 April – James Campbell Walker, architect (died 1888)
• 26 April – Robert Adamson, pioneer photographer (died 1848)
• 16 June – Old Tom Morris, golfer (died 1908)
• 19 June – George Whyte-Melville, sporting novelist (died hunting 1878 in England)
• 1 August – James Gowans, architect (died 1890)
• 17 October – Alexander Gardner, photographer (died 1882 in the United States)
• 13 December – Joseph Noel Paton, painter (died 1901)
• 29 December – John Francis Campbell, Celtic folklorist and inventor (died 1885 in France)

• 2 April – James Gregory, physician (born 1753)
• 15 June – John Ballantyne, publisher (born 1774)^[4]
• 4 October – John Rennie the Elder, civil engineer (born 1761; died in London)
• 8 November – Charles Murray, actor (born 1754 in England)
• 6 December – John Taylor, medical missionary (died in Persia)
• Isabel Pagan, poet (born c.1741)

• John Galt's novels Annals of the Parish and The Ayrshire Legatees are published.
• Jane Porter's novel The Scottish Chiefs is published.
• Sir Walter Scott's novel Kenilworth is published anonymously.

• 1821 in Ireland