Which American company is the largest publicly traded investment conglomerate by market capitalization?

Berkshire Hathaway is the largest publicly traded investment conglomerate by market capitalization. It owns operating businesses and large stakes in publicly traded companies, making its valuation different from that of a single-industry corporation.

Warren Buffett has served as Berkshire Hathaway's chairman and chief executive since 1965. Under his leadership, the company grew from a struggling textile manufacturer into a diversified group with insurance, rail transportation, energy, manufacturing, retail, and investment operations.

Insurance is central to Berkshire's structure. Its insurers collect premiums and hold investable funds known as “float” until claims are paid. Berkshire has used this capital, together with operating earnings, to acquire businesses and purchase stocks.

Berkshire's Class A shares are famous for their very high per-share price, while Class B shares were created to make ownership more accessible. Market capitalization counts both share classes, so the company’s overall value is not represented by the price of only one share.