The Queensland Railways 4D11½ Abt class locomotive was a class of 0-4-2RT steam locomotives operated by the Queensland Railways.

In October 1898, two Dübs & Co locomotives entered service.

Per Queensland Railway's classification system they were designated the 4D11½ Abt class, the 4 representing the number of driving wheels, the D that it was a tank locomotive, and the 11½ the cylinder diameter in inches.

They were built to assist conventional locomotives up and down a steeply graded rack railway section of the Central Western line at Mount Morgan.

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