Which position has Warren Buffett held?

Warren Buffett held the position of Chief Executive Officer at Berkshire Hathaway since 1970.
A chief executive officer (CEO), also known as a central executive officer, chief administrative officer (CAO) or chief administrator (CA) or just chief executive (CE), and as managing director (MD) in the UK, is one of a number of corporate executives charged with the management of an organization – especially an independent legal entity such as a company or nonprofit institution.