Aaron Helmer Sele (born June 25, 1970) is an American former Major League Baseball (MLB) right-handed pitcher. Sele debuted with the Boston Red Sox in 1993. He was traded to the Texas Rangers after the 1997 season and was named to the All-Star team in 1998. He signed as a free agent with the Seattle Mariners in 2000 and became an All-Star for the second and final time that season. He later pitched for the Anaheim Angels, Los Angeles Dodgers, and New York Mets before retiring after the 2007 season. Sele won 15 or more games in four consecutive seasons from 1998 to 2001. His 69 wins in those four years led the American League, but during that stretch he had no wins and 6 losses in the postseason, the most losses for an MLB pitcher without a postseason win.

Sele grew up in Poulsbo, Washington on the Kitsap Peninsula. He first started playing baseball in North Kitsap Little League. He attended North Kitsap High School, pitching on the baseball team. He helped lead the North Kitsap Vikings to the 1988 state championship.

Sele was drafted out of high school in the 37th round by the Minnesota Twins, but he chose to attend Washington State University where he played college baseball for the Cougars and head coach Bobo Brayton. Future MLB player Scott Hatteberg was in the same recruiting class as Sele. Sele and Hatteberg won three regular season Pac-10 titles in their three years in Pullman. In his first season in college, Sele went 6–5 with 3 saves, starting 8 of his 18 pitching appearances.

In Sele's sophomore season in 1990, the Cougars ended the season ranked 18th in the nation. Sele finished with a 12–3 with a 2.22 earned run average (ERA). He was named a first-team All-American by the American Baseball Coaches Association and third-team All-American by Baseball America. His 121 strikeouts, 10 complete games, and 121+2⁄3 innings pitched all rank second for a single season in school history. That summer, Sele pitched for Team USA, with Hatteberg again his teammate. On July 24, he pitched a three-hit shutout against Cuba with eight strikeouts. Sele led the American collegiate national team with 5 wins, 10 starts, 53 strikeouts, and 52 innings pitched.

In 1991, Sele went 8–6 with a 2.82 ERA for Washington State. He was named to the Pac-10 All-Conference First Team for the second consecutive year. He is the school leader with 278 strikeouts and is in the top 10 in wins, complete games, and innings pitched.

The Boston Red Sox selected Sele in the first round with the 23rd overall pick of the 1991 Major League Baseball draft. He received a $221,000 signing bonus. That summer he pitched for the Winter Haven Red Sox, going 3–6 with a team-high 4 complete games. He also pitched in the Florida Instructional League. He was a co-winner of the Tony Latham Memorial Award for a Red Sox player with the most enthusiasm. Sele advanced quickly through the Red Sox minor league system, pitching for the Class-A Advanced Lynchburg Red Sox and Double-A New Britain Red Sox in 1992. He had a combined 15–6 record with a 3.60 ERA and 141 strikeouts in 160 innings.

Before the 1993 season, Sele was ranked as the 84th best prospect by Baseball America, slightly worse than his ranking of 73rd the previous season. Sele began his third professional season with the Triple-A Pawtucket Red Sox. In his first start on April 10, he allowed no runs and one hit in 7 innings. With Pawtucket, he was 8–2 with a 2.19 ERA in 14 starts.

Sele joined the Red Sox on June 22 after ace Roger Clemens was placed on the disabled list. Sele made his major league debut the following night, allowing 1 run in 7 innings in a win over the Minnesota Twins. He struck out future Hall of Famer Dave Winfield for his first MLB strikeout. Sele was 6–0 with a 2.72 ERA in his first 8 starts for Boston. He was the third Red Sox rookie to ever win his first 6 decisions. His personal win streak ended on August 12 against the New York Yankees.