The Mecklenburg T 3 was a German, goods train, tank locomotive built for the Grand Duchy of Mecklenburg Friedrich-Franz Railway (Großherzoglich Mecklenburgische Friedrich-Franz-Eisenbahn) from 1884.
Originally designated as the Class XVII it had an 0-6-0T wheel arrangement and was based on the Prussian T 3.
These engines were later taken over by the Deutsche Reichsbahn as DRG Class 89.80 and incorporated into their renumbering plan.
Of these, 51 (the so-called T 3a) corresponded to the older version of the Prussian T 3 with a regulator on top.
They were employed primarily on branch line and shunting duties.