Professor Frank Matthews Leslie FRS[1] FRSE (8 March 1935 – 15 June 2000) was a Scottish mathematical physicist specializing in continuum mechanics.

His maternal grandfather Frank Rollo Matthews (1860 to 1921) was a bibliophile, acquiring a considerable library that the family treasured.

In December 1965 his important paper "Continuum theory of Liquid Crystals" appeared in Proceedings of the Cambridge Philosophical Society (60:949–55) in which he posited a "director" vector field characterizing an anisotropic fluid.

As Chandrasekhar writes, "...the formulation of general conservation laws and constitutive equations describing the mechanical behaviour of the nematic state is due to Ericksen and Leslie.

"[4] In the mid 1970s he consulted for Defence Evaluation and Research Agency at Malvern, Worcestershire with Cyril Hilsum in support of British LCD industries.

[5] His proposers were George Eason, Robin Knops, Donald Pack, David Butler, John N. Sherwood and Ian Sneddon.