<p>This thesis examines the alchemical patronage of Sir William Cecil, Lord Burghley (1520-1598), Principal Secretary and later Lord Treasurer to Queen Elizabeth I. Through an examination of Cecil's surviving papers, along with other primary manuscript and printed works, it places Cecil's patronage of alchemy within the context of both his previous examined patronage and the intellectual context of sixteenth century England. This thesis analyses why Cecil, a key member of government for over fifty years and Elizabeth's most trusted councillor, believed in the legitimacy of alchemical solutions to both national and personal problems. To explain Cecil's trust in alchemy, the thesis focuses first on his understanding of nature. It argues that a belief in alchemical transmutation was an essential consequence of an education that emphasised an Aristotelian understanding of the universe. Cecil was therefore receptive of demonstrations of theoretical as well as practical alchemical knowledge. Through an assessment of Cecil's neglected medical patronage, the thesis also argues that he was amongst the first in England to utilise new alchemically based medical treatments. In his role as Elizabeth's chief minister, Cecil administered a number of alchemical projects intended to support both Crown finances and England's industrial competitiveness. In light of Cecil's integral role in these projects, the thesis contends that he saw alchemy as a legitimate method of addressing both his short and long term policy aims. This thesis therefore both provides a more complete understanding of Cecil's patronage and adds to the limited historiography of alchemy in Elizabethan England.</p>