Vatasseri Parameshvara (* 1370 in Kerala, † 1460 ) was an Indian mathematician, astrologer and astronomer. He is one of the founders of the Kerala school of mathematicians and astronomers in South India.
He was a Nambudiri Brahmin ( his surname was Vatasseri ) and disciple of Madhava. His family came from Alathiyur on the banks of Bharathapuzha at Tirur ( Malappuram (District) in Kerala ). His son Damodara was also an astronomer and mathematician. He was the teacher of Nilakantha Somayaji, but also knew Parameshvara personally.
From him at least 25 manuscripts on astronomy are known. Among other things, he wrote commentaries on the works of Bhaskara I and Aryabhata I.
He was an observational astronomer who proposed based on close observations of eclipses over 55 years of corrections to the parameters in the then prevalent in India astronomical theories (especially of Aryabhata I. ).
He gave a formula for the radius of the circumscribed circle in the cyclic quadrilateral (usually Simon Lhuilier 1782 attributed ) and used a mean value theorem for the interpolation of the sine.