Lincoln is a constituency^{[n 1]} in Lincolnshire, England represented in the House of Commons of the UK Parliament since 2019 by Karl McCartney, a Conservative Party politician.^{[n 2]}

Since the split of the City of York seat with effect from the 2010 general election, Lincoln has been the oldest constituency in continuous existence in the UK – established in 1265. Lincoln was a bellwether between 1974 and 2017. The seat bucked the national Conservative victory in 1970 by electing a Labour MP, as it did in 2017.

The seat has been considered relative to others an ultra-marginal seat, as well as a swing seat, since 2005 as its winner's majority has not exceeded 6.9% of the vote since the 12.5% majority won in 2005 and the seat has changed hands three times since that year.

1885–1918: The existing parliamentary borough, and the parish of Bracebridge.^[2]

1918–1950: The County Borough of Lincoln, and the Urban District of Bracebridge.

1950–1974: The County Borough of Lincoln.

1974–1983: As prior but with redrawn boundaries.

1983–1997: The City of Lincoln, and the District of North Kesteven wards of Bracebridge Heath, North Hykeham Central, North Hykeham North, North Hykeham South, Skellingthorpe, and Waddington West.

1997–2010: The City of Lincoln, and the District of North Kesteven ward of Bracebridge Heath.

2010–2023: The City of Lincoln, and the District of North Kesteven wards of Bracebridge Heath and Waddington East, and Skellingthorpe.

2023–present: Following a local government boundary review in the District of North Kesteven which came into effect in May 2023,^[3][4] the constituency now comprises the following:

• The City Of Lincoln.
• In the District of Kesteven: the Bracebridge Heath ward; the majority of the Skellingthorpe & Eagle ward; and the majority of the Waddington Rural ward.^[5]

The constituency, as its name suggests, covers the cathedral city^{[n 3]} of Lincoln in Lincolnshire, and most of its directly adjoining villages.

Lincoln first sent Members to Parliament in 1265, thirty years before the first all-over coverage of cities and qualifying towns was introduced in the Model Parliament, and has done so ever since, although no records exist from before the end of the 13th century. The early elections were held at the Guildhall and the burgesses elected were usually officials of the borough.

The representation, originally two Members ("burgesses"), was reduced to one Member in 1885.

The seat was represented for five years by former Cabinet minister Margaret Jackson, later Margaret Beckett.^{[n 4]} Lincoln became the oldest constituency in the country in 2010 when the City of York constituency was divided.

The seat includes the University of Lincoln. From 1945 to 1972 Lincoln was continuously held by the Labour Party, often as a safe seat. The city has good transport links with Nottingham, Hull and the smaller ancient market towns in Lincolnshire, such as Spalding, Market Rasen and Boston. Lincoln was a bellwether constituency from October 1974 to 2015, voting for the party which would form the government in each election. In 2017 Labour took the seat despite being the 2nd largest party nationwide.

• List of parliamentary constituencies in Lincolnshire