Class 91

Class 91 may refer to:
 * British Rail Class 91
 * DRG or DR Class 91 2-6-0T tank locomotives with the Deutsche Reichsbahn:
 * Class 91.0-1: Prussian T 9.2, BLE Nos. 36 to 43, PKP Class TKi2


 * Class 91.3-18: Prussian T 9.3
 * Class 91.19: Mecklenburg T 4
 * Class 91.20: Württemberg T 9


 * KTM Class 91
 * South African Class 91-000
 * CFR (Romanian Railways) Class 91 (now reclassified as class 98 )