Percy Ireland Lathy (1874 – 8 September 1943) was an English entomologist who specialised in butterflies.

Lathy was first assistant to William Watkins, in Eastbourne then curator for Herbert Jordan Adams in Enfield (this collection is now in the Natural History Museum, London).

At this time, on Adams' behalf, he collected in the West Indies (especially Jamaica) and South America and employed collectors who were sent to Peru and Dutch New Guinea.

After Adams' death in 1912, he worked for Cabinet Le Moult in Paris then for Aimée Fournier de Horrack.

Aimée Fournier de Horrack was a leading figure in literary and musical circles and had a private butterfly collection containing very rare and expensive species of Morpho, Agrias, Catagramma, Prepona, Papilionidae, Ornithoptera, Charaxes, Riodininae and Lycaenidae.