The 1948 United States Senate election in Texas was held on November 2, 1948. After the inconclusive Democratic Party primary in July, a hotly contested runoff was held in August in which U.S. Congressman Lyndon B. Johnson was officially declared to have defeated former Texas governor Coke R. Stevenson for the party's nomination by eighty-seven votes. The state party's executive committee subsequently confirmed Johnson's nomination by a margin of one vote. The validity of the runoff result was challenged before the U.S. Supreme Court due to allegations of irregularities, and in later years, testimony by the parties involved indicated that widespread fraud occurred and that friendly political machines produced the votes needed for Johnson to defeat Stevenson. After years of desultory opposition to Democrats during the post-Reconstruction years of the Solid South, Republicans vigorously contested the general election by nominating businessman and party activist Jack Porter, who waged an aggressive campaign. Johnson won his first term in the Senate, but by a closer margin than usual for Texas Democrats.

Lyndon Baines Johnson, often referred to by his initials LBJ, was an American politician who served as the 36th president of the United States from 1963 to 1969. He became president after the assassination of John F. Kennedy, under whom he had served as the 37th vice president from 1961 to 1963. A Democrat from Texas, Johnson also served as a U.S. representative and U.S. senator.