Ayanava Province was a geographic region of the planet Mestiko. It was a remote region of the planet which included the Ayanava and Nehdi Valleys, and was home to the Nehdi and Alangabi tribes. Although considered by some to be a backwards region, Ayanava Province generated two laureates in the sciences, as well as Rhilnam, the famed performance artist.
Ayanava Province was once of the regions directly hit by the radiation blast from the rogue pulsar that passed through the Mestiko system in 2265. Despite this, the Payav of Ayanava refused to relocate after "the Pulse", and worked hard to reclaim their land so as not to be dependent on government aid.
In 2293, an epidemic began killing the young people of Ayanava Province, and Dr. Leonard McCoy traveled there to investigate. With the help of Commander Uhura, he discovered the disease was caused by bioweapons developed by the Alangabi for use against the Nedhi circa 2243, which had leaked into the water table after being buried and forgotten. (TOS - Mere Anarchy eBook: Its Hour Come Round)