The GNRI BUT Class was a fleet of diesel-powered railcars operated by the Great Northern Railway Board and its successors between 1957 and 1980.

Unassembled bodies (designed by Park Royal), underframes and mechanical parts were shipped to the GNRB's workshops in Dundalk in the summer of 1956, where final assembly took place.

Upon the dissolution of the GNRB in 1958, fourteen of the BUTs passed to the Ulster Transport Authority (UTA), and the other ten to Córas Iompair Éireann (CIÉ).

Following withdrawal, NIR discovered that the BUTs contained asbestos, so along with other stock they were disposed of at Crosshill quarry near Crumlin, County Antrim.

The other sixteen were built with a half-cab at each end to the left of the corridor connection, and accommodation for 56 second-class passengers, although they had no guard's or luggage compartment.

However, compatibility with the earlier AEC railcars and regular coaching stock was hindered by the fact that they utilised an unusual type of corridor connection.