The SECR J class was a class of 0-6-4T steam tank locomotive built for heavy freight service on the South Eastern and Chatham Railway, by Harry Wainwright.

The South Eastern and Chatham Railway (SECR) had a need for versatile mixed traffic locomotives which could accelerate quickly so as not to impede the heavy passenger traffic on the densely used lines around London.

Following the success of his C class 0-6-0 and his H class 0-4-4T Harry Wainwright sought to combine their good features but was limited by weight restrictions on many lines.

The class were moderately successful on a variety of secondary passenger and freight services.

However, all but number 597 were renumbered by the Southern Railway in 1927/8 to create a unified sequence from A596 to A599.