As of August 2015, Warren E. Buffett owns the most shares of Berkshire Hathaway class A stock, according to Morningstar. Buffett's 321,000 shares account for 19.64 percent of the total amount of shares.
The major owners of Berkshire Hathaway shares are institutions, insiders and mutual funds, according to Morningstar. An institution, Fidelity Management and Research Company, is the next biggest owner after Buffett, with 29,193 shares and 1.79 percent of the total amount. Fidelity Contrafund tops the list of fund owners, with 23,897 shares and 1.46 percent of the total amount. Two other institutions that hold at least 1 percent of the total amount of shares are Barnes, Bonner, Castles and Capital World Investors.