The A45 is a major road in England. It runs east from Birmingham past the National Exhibition Centre and the M42, then bypasses Coventry and Rugby, where it briefly merges with the M45 until it continues to Daventry. It then heads to Northampton and Wellingborough before running north of Rushden and Higham Ferrers and terminating at its junction with the A14 road near Thrapston.
The road used to run to Felixstowe but most of the route was re-designated as the A14 in the mid-1990s.

Birmingham to Coventry
The former route of the A45 through Coventry exits at a junction as the A4114, in the part of Coventry called Allesley, the western end of the Coventry bypass. At the staggered junction with the B4101, there is the factory of Massey Ferguson, now owned by TRW, and a Sainsburys supermarket in Tile Hill. The road passes over the West Coast Main Line, then enters Canley near a roundabout which is the main exit for the University of Warwick. There is a traffic-light junction with the A429, heading to Kenilworth. There is a roundabout with the B4113, then a GSJ with the A46 and A45. This busy section has many speed cameras and overlaps with the A46. The next roundabout near Tollbar End, called the Tollbar Island, is one of the busiest in the Midlands. It has exits for the A46 north/Coventry Eastern Bypass, Coventry Airport, and B4110, the former route of the A45. There are plans to build a GSJ here - the A45 will go under the other roads.
Where the road crosses the River Avon, the road re-enters Warwickshire. The A423 exits to the south-east at a GSJ near the UK factory of Peugeot. The main road from Warwick, the A445, meets near Ryton-on-Dunsmore at traffic lights. This section has many speed cameras. Further east, there is a roundabout with the B4455, the Fosse Way. There is a grade separated junction ("GSJ") with the main road for Rugby, the A4071, and the B4453. There is a Texaco garage here. The next roundabout near Thurlaston used to be very busy before 1972, when the M6 opened. It is now the start of the M45. The former A45 passes through Dunchurch as the B4429. A junction was built on the M45 in 1991 to allow traffic to head south-east onto the A45, and to alleviate traffic congestion in Dunchurch.

Coventry to Dunchurch
Heading towards Daventry, the road is fairly wide and single-carriageway. The road passes a prison at Rye Hill and a Young Offender Institution next to it at Onley. After Willoughby, the road enters Northamptonshire, where it crosses the Oxford Canal and Grand Union Canal near Braunston. The Jurassic Way crosses the road here. The road enters Daventry, home to large distribution centres for Ford Motor Company, Tesco and Diageo. The road briefly runs concurrent with the A425 heading to Leamington Spa, then heads south-east on the Daventry bypass, called the Stefen Way. The road meets the B4038 at a roundabout where the A425 exits. The road heads west past Dodford to Weedon Bec, where it crosses the West Coast Main Line and Grand Union Canal, then meets the A5 at traffic lights. The road passes through Flore, then meets the M1 at junction 16.

Dunchurch to M1 at Northampton
Until 2004, the route of the A45 headed east along the dual-carriageway from junction 16 towards Northampton, but now it has been diverted to follow the M1 south, then to join with the route of the A508 north from junction 15, to join the main flow of traffic on the Northampton bypass. Although slightly longer this route involves fewer roundabouts. From the point as which it meets the old route at the A45/A508 GSJ, near Northampton High School, it crosses the River Nene and Nene Way, then there is a large GSJ with the A428. This section is the Nene Valley Way, and overlaps with the A43, which exits at a GSJ near Weston Favell. The GSJ with the A5076 is also the exit for Billing Aquadrome.
The former route of the A45 to Wellingborough is now the A4500. The road has a GSJ with the B573 near Earls Barton, which has a famous Saxon church. The road meets the Wellingborough bypass (A509) at a roundabout. It runs concurrently with the A509 to the GSJ near the bridge over the River Nene, where the A509 exits south near Irchester Country Park.
East of Wellingborough, the road crosses the Midland Main Line. There is a GSJ for the A5001, which heads to Rushden. There is then a roundabout with the A5028. This is the point where the new road (post-A14), heads north-east rather than due east. The old route, now the B645, heads through Higham Ferrers, which is now bypassed by the A45. The bypass runs alongside the River Nene. At the roundabout with the A6 near Irthlingborough, it starts the follow the former route of the A605. The section of dual carriageway from the M1 now ends at the next roundabout. This is the start of the Raunds bypass. The next roundabout is with the B663. The route bypasses Ringstead and the A45 finishes at a GSJ with the A14 near Thrapston.

Annexed section
The original (1923) route of the A45 was Birmingham to Ipswich. The road was extended to Felixstowe in 1935, replacing the A139.
When the new A14 A1-M1 link road was opened to traffic in the mid-1990s, the Cambridge to Felixstowe stretch of the A45 was redesignated as the A14; from the former A605 to the A1 it was downgraded to B645; and from the A1 to Cambridge it became part of an extended A428.