The M45 is a motorway in Northamptonshire and Warwickshire, England and is 7.9 miles (12.7 km) long. It runs between junction 17 of the M1 motorway south east of Rugby and a junction with the A45 road southwest of Rugby. It has one of the lowest traffic volumes of the United Kingdom motorway system.

The M1 motorway connects London to Leeds, where it joins the A1(M) near Aberford, to connect to Newcastle. It was the first inter-urban motorway to be completed in the UK; the first motorway in the country was the Preston Bypass, which later became part of the M6.