Alec Trendall (8 December 1928 – 4 April 2013^[1][2]) was an English geologist, poet, and explorer. He is known for his work in mapping the island of South Georgia and for surveying the geology of Western Australia.

Alec Trendall was born in 1928 at Enfield, Middlesex, and in 1949 graduated in geology at London University. He has a PhD degree from Liverpool University.^{[citation needed]}

Trendall was the geologist on the 1951–52 and 1953-54 South Georgia Survey expeditions led by Duncan Carse. Trendall Crag, 1,005 m, overlooking the north side of Drygalski Fjord at the southeast end of South Georgia, was named to commemorate Alec Trendall's contribution. In 2011 he published a full account of the survey expeditions, entitled Putting South Georgia on the Map.^[3]

The Scott Polar Research Institute's digitised archive includes 305 images of Trendall^[4] including images of a bergschrund - a hole in an ice sheet - which Trendall fell down before being carried on an improvised sled,^[5] to leave the First expedition.

Trendall was Director of the Geological Survey of Western Australia from 1969-1989.^[6] Trendall discovered the locality known as Trendall Reserve, Eastern Pilbara in 1984. It contains convincing evidence of some of the oldest known fossils known as stromatolites.^[7]