Willard Wayne Terwilliger (June 27, 1925 – February 3, 2021), nicknamed "Twig", was an American professional baseball second baseman. He played nine seasons in Major League Baseball (MLB) between 1949 and 1960 for the Chicago Cubs, Brooklyn Dodgers, Washington Senators, New York Giants, and Kansas City Athletics.

Terwilliger grew up in Michigan. He joined the Marines in 1943 following his 18th birthday and served as a radioman on an amphibious tank in the Pacific Theater of World War II.

While overseas, Terwilliger served in Tinian and Iwo Jima, and had his tank destroyed at Saipan. "We were hit and the tank bogged down," he told The Sporting News on April 26, 1950. "We had to abandon the tank. Everybody scattered into the nearest fox holes. But at just about that time a [Japanese] tank rolled up and began blasting away. I knew I had to get out of there, so I ran for the beach, zigzagging in and out with the tank chasing me. I'm sure I'd be lying out there somewhere now if it hadn't been for one of our own tanks, which luckily showed up while I was doing all that broken field running."

Terwilliger was discharged in late 1945 and attended Western Michigan College, where he quickly became a star shortstop. As early as 1946, he was attracting attention from major league scouts, and St. Louis Browns' scout Jack Fournier was particularly keen to sign him.

In 1948, after finishing college, Terwilliger was playing second base with the semi-pro Benton Harbor Buds when he was signed as a free agent in July by the Chicago Cubs. The Cubs assigned him to the Single-A Des Moines Bruins of the Western League, where he finished the season. In 1949, Terwilliger was promoted to the AAA Los Angeles Angels of the Pacific Coast League, where he batted .275 in 115 games, before being called up to the Cubs in August and playing in 36 games. Terwilliger spent the 1950 season as the Cubs' starting second baseman, hitting .242 with 10 home runs, 32 RBI, and 13 stolen bases. However, after getting off to a poor start to the 1951 season, Terwilliger was included in a trade that sent outfielder Andy Pafko, pitcher Johnny Schmitz, and catcher Rube Walker to the Brooklyn Dodgers for catcher Bruce Edwards, pitcher Joe Hatten, outfielder Gene Hermanski and infielder Eddie Miksis.

After spending the 1952 season with the AAA St. Paul Saints, Terwilliger was claimed off waivers by the Washington Senators following the 1952 season and spent the next two seasons as the Senators' second baseman. Prior to the start of the 1955 season, Terwilliger switched teams again after the New York Giants purchased him from the Senators. He spent the 1955 and '56 seasons shuttling between New York and AAA Minneapolis and the entire 1957 season at AAA. Following the 1957 season, he was traded to the Detroit Tigers in a swap for fellow journeymen infielder Jack Dittmer.

After spending 1958 with the Tigers' AAA Charleston Senators, he was acquired by the Kansas City A's from the Detroit Tigers in the December 1958 Rule 5 draft. In 1959, Terwilliger saw his last large stretch of time in the majors, playing 74 games at second and shortstop for the A's. After starting the 1960 season with the A's, Terwilliger was unofficially traded to the New York Yankees, a transaction that was common at the time between the two teams when the Yankees were accused of using the A's as a major league farm club and the two teams often seemed to have mutual rights to each other's players, and played the rest of the season at AAA Richmond Virginians before retiring as a full-time player.

In 666 games over nine seasons, Terwilliger posted a .240 batting average (501-for-2091) with 271 runs, 22 home runs, 162 RBI and 247 bases on balls. Defensively, he recorded a .974 fielding percentage playing primarily at second base.