Kenneth Allen Phelps (born August 6, 1954) is an American former professional baseball designated hitter and first baseman. He played for six different Major League Baseball (MLB) teams from 1980 to 1990, primarily with the Seattle Mariners. Baseball statistician Bill James cited Phelps as an example of a player who was unfairly denied a chance to play in the majors, despite compiling strong minor league statistics.

Born and raised in Seattle, Washington, Phelps graduated from Ingraham High School in north Seattle in 1972. He played a year at Washington State in Pullman under Bobo Brayton, then headed to Mesa Community College, looking for an opportunity to play at Arizona State in Tempe.

In his only season at MCC in 1974, Phelps was named a junior college All-American. He was drafted twice in the first round (January and June drafts) by the New York Yankees and Philadelphia Phillies, respectively. He had previously been drafted out of high school by the Atlanta Braves in the eighth round (179th overall) of 1972 Major League Baseball draft.

All this earned Phelps a chance from Coach Jim Brock to play at ASU, where he was named to the College World Series All Star team in 1976, when the Sun Devils lost to rival Arizona after having defeated the Wildcats seven times that season, including a first-round game in Omaha.

The left-hitting first baseman was selected by the Kansas City Royals in the 15th round (354th overall) of the 1976 Major League Baseball draft. Phelps hit a combined 43 home runs from 1980–81 for the Omaha Royals, KC's Triple-A affiliate in the American Association. On September 20, 1980, he made his major league debut against the Oakland Athletics, appearing as a defensive replacement in the seventh inning and grounding out in his only at bat. Phelps appeared in 24 career games with Kansas City, posting a .115 batting average and one RBI.

In January 1982, the Royals traded Phelps to the Montreal Expos in exchange for pitcher Grant Jackson. In the American Association in 1982, Phelps hit .333 with 46 home runs and 141 RBI in 132 games for the Triple-A Wichita Aeros. He had only eight major league at bats that year, as there was no room on a very talented Montreal roster for Phelps to break in. Instead, Phelps' hometown club, the Seattle Mariners, purchased him from the Expos on March 30, 1983.

An average defensive player, Phelps was better suited to play with the Mariners, as he could serve as the designated hitter, and the struggling franchise also had plenty of room for advancement. Phelps split time in 1983 between Seattle and its Pacific Coast League farm club, the Triple-A Salt Lake City Bees. Again, he hit minor league pitching well (.341 with 24 home runs and 82 RBI in 74 games), but he did not play much in the majors (.236, seven home runs and 16 RBI in 50 games).

In 1984, Phelps played in 101 games, batting .241 while hitting 24 home runs and recording 51 RBI in only 290 at-bats. Bad luck intervened early that year when a pitch broke his hand in the third game of the season; he had won the regular first base job, and hit two home runs in his first three-game and had five hits in his first ten at-bats. The injury resulted in the call-up of first baseman Alvin Davis after just one game in Triple-A, who immediately produced; Davis was named to the American League All-Star team and was the league's Rookie of the Year.