Brian Winfield Sipe (born August 8, 1949) is an American former professional football player who was a quarterback for the Cleveland Browns of the National Football League (NFL) from 1974 to 1983. He then played in the United States Football League (USFL) for two seasons.

Sipe was born and raised in California. He competed in the 1961 Little League World Series for El Cajon, California, and attended Grossmont High School. Although mostly sidelined for the first several years of his NFL career, Sipe was eventually recognized as one of the better quarterbacks in Browns history, winning the league's Most Valuable Player Award in 1980. He was a college football star under head coach Don Coryell at San Diego State University, where he studied architecture and became the team's quarterbacks coach in 2009, remaining in that role for five years, through 2014.

Drafted in the thirteenth round of the 1972 NFL draft by the Cleveland Browns, Sipe spent the first two years of his career as a member of the teamʼs reserve squad, seeing no action on the field.

In 1974, Sipe started four games after helping the Browns come back from a 12-point deficit against the Denver Broncos on October 27. However, after winning just one of these four contests (a 21–14 victory against the New England Patriots on November 11), he was replaced by Mike Phipps.

The team's disastrous 1975 season saw Sipe enter the starting lineup after three consecutive losses in which the Browns were outscored 124–26. Sipe's three starts saw the Browns become more competitive, but still resulted in a trio of defeats, sending him back to the sidelines. The following year, he finally moved into a consistent starting role following an opening game injury to Phipps on September 12, 1976. As the team's signal caller that season, he led them to a 9–5 record, a six-game improvement over the previous season. 1976 was the team's second year under head coach Forrest Gregg.

During the first half of the 1977 season, Sipe led the team to five wins in their first seven games. However, on November 13 of that year, Sipe suffered a season-ending shoulder injury at Three Rivers Stadium against the Pittsburgh Steelers in the second quarter of the team's 35–31 defeat. With Phipps gone to the Chicago Bears, the Browns turned to back-up quarterback Dave Mays, who went 1–3 as a starter. The 1977 season also saw a head coaching change as Gregg was fired and defensive coordinator Dick Modzelewski took over for the final game. Sipe came back the following year to throw for more than 2,900 yards and 21 touchdown passes, but the team's overall inconsistency resulted in an 8–8 finish.

Serving as the catalyst for many thrilling moments during the 1979 and 1980 seasons, Sipe helped the team earn the nickname "Kardiac Kids." The designation was in recognition of their tendency to produce heart-stopping comeback victories in the final minutes of many games. Over the course of these two seasons, Sipe led the Browns to eight comebacks and eleven game-winning drives in the fourth quarter or overtime.

Sipe led Cleveland to a 4–0 start in 1979, including a season opening overtime win over the New York Jets.