John William Davis (April 13, 1873 – March 24, 1955) was an American politician, diplomat and lawyer. He served under President Woodrow Wilson as the Solicitor General of the United States and the United States Ambassador to the United Kingdom. He was the Democratic nominee for president in 1924 but lost to Republican incumbent Calvin Coolidge.

Davis was born and raised in West Virginia, where his father, John James Davis, had been a delegate to the Wheeling Convention and served in the U.S. House of Representatives in the 1870s. Davis joined his father's legal practice and adopted many of his father's political views, including opposition to anti-lynching legislation and support for states' rights. Davis served in the U.S. House from 1911 to 1913, helping to write the Clayton Antitrust Act. He held the position of solicitor general in the Justice Department from 1913 to 1918, during which time he successfully argued for the unconstitutionality of the grandfather clause in Oklahoma's constitution, which had a discriminatory effect against African-American voters, in Guinn v. United States.

While serving as ambassador to Britain from 1918 to 1921, Davis was a dark horse candidate for the 1920 Democratic presidential nomination. After he left office, Davis helped establish the Council on Foreign Relations and advocated for the repeal of Prohibition. The 1924 Democratic National Convention nominated Davis for president after 103 ballots. He remains the only major party presidential nominee from West Virginia. Running on a ticket with Charles W. Bryan, Davis lost in a landslide to incumbent President Coolidge. Davis did not seek public office again after 1924.

He continued as a prominent attorney, associated with several law firms over the years, and represented many of the largest companies in the United States from the 1920s onwards. Davis argued 140 cases before the U.S. Supreme Court.

In addition to his legal work, Davis was also involved in the New York City Bar Association, serving as its president from 1931 to 1933. In 1933, he represented J.P. Morgan, Jr. and his companies during a Senate investigation into private banking and the causes of the Great Depression. During the last two decades of his career, Davis represented large corporations before the Supreme Court, challenging the constitutionality and application of New Deal legislation. He lost many of these cases but he scored a major victory in Youngstown Sheet & Tube Co. v. Sawyer (1952), in which the Supreme Court ruled against President Harry Truman's seizure of the nation's steel plants. Davis unsuccessfully defended the "separate but equal" doctrine in Briggs v. Elliott (1952), one of the companion cases to Brown v. Board of Education (1954), in which the Court ruled that segregated public schools were unconstitutional.