David Martin Scott Steel, Baron Steel of Aikwood, (born 31 March 1938) is a retired British politician. Elected as Member of Parliament for Roxburgh, Selkirk, and Peebles, followed by Tweeddale, Ettrick, and Lauderdale, he served as the final leader of the Liberal Party, from 1976 to 1988. His tenure spanned the duration of the alliance with the Social Democratic Party, which began in 1981 and concluded with the formation of the Liberal Democrats in 1988.

Steel served as a Member of the UK Parliament for 32 years, from 1965 to 1997, and as a Member of the Scottish Parliament (MSP) from 1999 to 2003, during which time he was the parliament's Presiding Officer. He was a member of the House of Lords as a life peer from 1997 to 2020. Steel resigned from the House of Lords after the Independent Inquiry into Child Sexual Abuse accused him of an "abdication of responsibility" over his failure to investigate allegations of child sex abuse against Liberal MP, Cyril Smith.