Glen Edward Day (born November 16, 1965) is an American professional golfer who plays on the PGA Tour.

Day was born in Mobile, Alabama, and raised in Poplarville, Mississippi, by his mother Jeanne Bass Day. Jeanne was widowed at the age of 28 when Glen was approximately 2 years of age. His grandfather Glyndol Bass, was young Glen’s primary male role model. Bass, an avid golfer and member at Pearl River Valley Country Club just outside Poplarville, started Glen playing golf when he was 2 to 3 years of age. By the age of 10, he held a 5 handicap and was able to regularly shoot par on 18 holes. He graduated from Poplarville High School in 1983, attended the University of Oklahoma, then turned professional in 1988. He has one sister, Danielle, and is married to the former Jennifer Ralston. They have two daughters, Whitney Elizabeth, born in 1994 and Francis Christina, born in 1996.

Day was the first golfer to win a professional tournament using the Nike Golf Ball by defeating Payne Stewart to win the 1999 MCI Classic played at the Sea Pines Plantation Harbor Town Golf Links, Hilton Head, South Carolina. In 2000, the first of two top-10s came at the first event of the season with a T-8 in the Mercedes Championship. In 2001, he came in 4th in the MasterCard Colonial, and tied for 6th in the AT&T Pebble Beach National Pro-Am. In his forties, Day split his playing time between the PGA Tour and the Nationwide Tour. He later joined the PGA Tour Champions after turning 50.

Day is also a golf course architect, forming Day-Blalock Golf Course Design with Alan Blalock in 1999. He has featured in the top 50 of the Official World Golf Rankings, peaking at 30th in 2000.

Day resides in Little Rock, Arkansas.