The British Rail Class 144 Pacer was a diesel multiple unit (DMU) passenger train built at Derby between 1986 and 1987. BR, seeking to procure improved derivatives of the earlier Class 141, placed an order with the manufacturers British Rail Engineering Limited (BREL) and Walter Alexander to construct their own variant, the Class 144. A total of 23 units were constructed.

All units have now retired from mainline service, though a significant proportion have been acquired for preservation on heritage railways and in other uses. 19 out of the 23 units have been purchased following withdrawal for this purpose, of which 15 units are in operational condition.