Coert or Court Lambertus van Beyma (Harlingen, 5 February 1753 - Dronrijp, 7 September 1820), son of Julius Matthijs van Beyma and Fokel Helena van Burmania, was a public notary and auctioneer, delegate and representative of the Frisian States, leader of the Frisian patriots. He was the initiator of a Frisian coup and spent time in exile in northern France. On his return to the Netherlands in 1795, he became a delegate to the National Assembly of the newly established Batavian Republic.
His father had been Secretary to the Admiralty of Friesland in Harlingen, and his mother equally descended from a Frisian noble grietman family. As a law student, Van Beyma gave a speech in 1769 during the visit of stadholder William V to Franeker. He continued his studies in 1774 at Leiden University. Court Lambertus became a delegate to the Frisian States in 1776. In 1780, he however failed to become the grietman of West-Dongeradeel, though he did achieve the position of Secretary. In that capacity, he corresponded with Joan van der Capellen tot den Pol. Together they planned petitions for the built-up of a provincial army, the recognition of the new United States of America and to restrict the power of the stadhouder. In February 1782 Van Beyma undertook an attempt in the Frisian States to put into practice article VIII of the Union of Utrecht, which would effectively allow for a general arming of the population. When Van Beyma in 1783 achieved a successful alliance between eight Frisian cities, the Patriots gained further influence and power. Through the development of a fixed time-table schedule, the important posts within the Provincial States were subsequently attributed in a more democratic manner.