Mandayam Osuri Tirunarayana Iyengar (6 February 1895 – 16 September 1972) was an Indian medical entomologist who worked on management of filaria and malaria vectors.

Alasingrachariar was a senior judge in the Madras High Court, and an older brother was the botanist M.O.P.

After studying at the Hindu High School and graduating from the Presidency College, Madras he joined as an entomologist in-charge in the Bengal Malaria Research laboratory in Calcutta from 1918.

[4][5] He worked under the aegis of the Rockefeller Foundation for the Travancore State between 1931 and 1934 studying filariasis on which he served as a consultant for the World Health Organization working in many parts of the world including Afghanistan,[6] the Maldives,[7] New Guinea,[8] Samoa, and Thailand.

A mermithid, named after him as Romanomermis iyengari has found continued use in the management of anophelines around the world.