The history of AT&T dates back to the invention of the telephone. The Bell Telephone Company was established in 1877 by Alexander Graham Bell, who obtained the first US patent for the telephone, and his father-in-law, Gardiner Greene Hubbard. Bell and Hubbard also established American Telephone and Telegraph Company in 1885, which acquired the Bell Telephone Company and became the primary telephone company in the United States. This company maintained an effective monopoly on local telephone service in the United States until anti-trust regulators agreed to allow AT&T to retain Western Electric and enter general trades computer manufacture and sales in return for its offer to split the Bell System by divesting itself of ownership of the Bell Operating Companies in 1982.

AT&T Inc. is an American multinational telecommunications holding company headquartered at Whitacre Tower in Downtown Dallas, Texas. It is the world's fourth-largest telecommunications company by revenue and the largest wireless carrier in the United States. As of 2023, AT&T was ranked 13th on the Fortune 500 rankings of the largest United States corporations, with revenues of $120.7 billion.