William Alexander Madocks (17 June 1773 – September 1828) was a landowner and Member of Parliament (MP) for the town of Boston in Lincolnshire from 1802 to 1820, and then for Chippenham in Wiltshire from 1820 to 1826. He is best known, however, for his activities as an agricultural improver in Gwynedd, especially around the towns of Porthmadog and Tremadog, both of which he founded.