William Lowther, 1st Earl of Lonsdale KG (29 December 1757 – 19 March 1844) was a British Tory politician and nobleman. Lowther was the son of Sir William Lowther, 1st Baronet. Lowther was briefly Member of Parliament for Appleby in 1780, for Carlisle from 1780 to 1784 and for Cumberland from 1784 to 1790. In 1807, Lowther was created Earl of Lonsdale. A coal magnate, he spent £200,000 on the Lowther estate and built a new Lowther Castle.