SEK (Sidirodromoi Ellinikou Kratous, Hellenic State Railways) Class Λβ (or Class Lb; Lambda-beta) is a class of 16 2-10-0 steam locomotives, ex-WD Austerity 2-10-0s purchased after the Second World War.

All of them were previously stabled in Egypt and were transported to Greece, as part of the UNRRA mission in Greece (arrived at Thessaloniki port on 16 January 1946).

They were mainly allocated to the Salonika division, but hauled both freight and passenger trains (including Athens to Istanbul Expresses) all across Greece, until they were slowly replaced by diesel locomotives until the mid-1970s, being one of the last classes of steam locomotives of SEK to be withdrawn from regular service.

A total of six Greek Austerity 2-10-0s survived the 1984-1985 steam locomotive scrappings,[1] two of which were repatriated to Great Britain.

Two continued to work tourist specials out of Drama until the mid-00s whilst the remaining two were left in open storage thereby leaving just four survivors in Greece and the two repatriated examples.