Illya is a unique and uncommon given name of Slavic origin, derived from the Greek name Hilarion, which means "cheerful" or "happy." It is typically pronounced as /ɪlˈiːə/ in English. This name has been predominantly used by males historically but can also be given to females. Illya is not particularly associated with any specific country, although it is more commonly found among Slavic-speaking populations. It is considered a unisex name in some cultures. Notable figures bearing this name include Ukrainian footballer Ilya Bliznuch and Russian ballet dancer Ilya Kuznetsov.
The name Illya peaked in popularity in 1966 with 11 births that year, while it had the same number of births as its lowest point, five, in both 1965 and 1968. Over these four years, there were a total of 31 babies named Illya.