Boston United Football Club is a professional association football club based in Boston, Lincolnshire, England. The club participates in the National League, the fifth level of the English football league system.

The club is known as 'the Pilgrims' in reference to the Pilgrim Fathers, who left England and sailed to North America and settled near, though did not found, Boston, Massachusetts. The club's crest features the pilgrim fathers' ship, the Mayflower. The club's traditional colours are amber and black. They are rivals with Lincoln City, Scunthorpe United, Gainsborough Trinity and Grimsby Town. They play at the Boston Community Stadium, which was completed in 2020 with a capacity of 5,061 (2,155 seated) spectators.

The club was formed in 1933 as a successor to the short lived Boston Town. They initially competed in the Midland League, before joining the Southern League for a four-year spell in 1958. They returned to the Midland League and then joined then United Counties League, winning their first league title in 1965–66. Boston then switched to the West Midlands (Regional) League, winning the Premier Division in 1966–67 and 1967–68, before becoming founder members of the Northern Premier League in 1968. United won four Northern Premier League titles in the 1970s (1972–73, 1973–74, 1976–77 and 1977–78) and became founder members of Alliance Premier League in 1979. Boston returned to the Northern Premier League in 1993 and moved back to the Southern League Premier Division in 1998.

Boston United won the Southern League in 1999–2000 and the Conference in 2001–02 to secure a place in the Football League for the first time under the stewardship of controversial manager Steve Evans. They spent five years in the fourth tier, but entered administration in 2007 and were relegated down two divisions into the Conference North. Demoted to the Northern Premier League the next year, Boston won the Northern Premier League Premier Division play-offs in 2010 and had five unsuccessful play-off campaigns in the Conference and National League North before winning the National League North play-offs in 2024.

The club was founded in 1933 as a successor to a club called Boston Town. Their first game was a 3–1 defeat at home to Grimsby Reserves on 26 August 1933, when a crowd of 1,544 watched Boston's no.7, Blessed, score United's first ever goal. They then had a moderate amount of success in various leagues, including the Midland League and Southern League.

The club's FA cup run of 1955–56 included a 6–1 victory at Derby County, then playing in Third Division North, with Geoff Hazledine scoring a hat-trick. This was a record away win by a non-League team against League opponents in the FA Cup. This set up a Third round match against Tottenham Hotspur of the Football League First Division at White Hart Lane on 7 January 1956. The match against Tottenham Hotspur was played in front of a crowd of 46,185. The Pilgrims lost 4–0, but the match was more notable for the travelling support. Over 10,000 Boston supporters attended the game. A number of special train services from Boston to King's Cross were set up for the day.

They were founder members of the Northern Premier League in 1968, of which they were champions four times, and of the Alliance Premier League (now the National League) in 1979. However, their Northern Premier League title wins were not enough to gain them election to the Football League, and when they won the title in 1978 they surprisingly missed out on league status in favour of runners-up Wigan Athletic, who took the Football League place previously held by Southport.

In 1985, Boston United went to Wembley for the first and only time in their history for the FA Trophy Final of the 1984–85 season, after Bob Lee scored a winning last minute goal in the 2nd leg of the semi-final against Altrincham at York Street to put the Pilgrims through. Boston lost 2–1 to Wealdstone in front of 20,775, with Chris Cook scoring United's only goal.