Daniel Hay du Chastelet (23 October 1596, Laval – 20 April 1671) was a French clergyman and mathematician.
He was the parish priest of Andouillé, doctor in theology at the Paris Faculty and abbot of Notre-Dame de Chambon Abbey.
He was also the Dean of the Saint-Tugal de Laval Collegial Church from 1621 to 1671 and prior of the Convent of the Augustins of Vitré.
He was nominated by the King to be the abbot of the abbey on February 23, 1623, a position left vacant for him by Georges de la Trémoille.
He wrote a considerable amount on mathematics, but his nephew the marquis Paul Hay du Chastelet, knowing nothing about the subject, allegedly burnt the writings.