William Alexander Madocks was a British politician and landowner who served as Member of Parliament (MP) for the borough 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 which he founded and which are named after him.

Boston was a parliamentary borough in Lincolnshire, which elected two Members of Parliament (MPs) to the House of Commons from 1547 until 1885, and then one member from 1885 until 1918, when the constituency was abolished.