Wittman was born on October 26, 1987 in Atlanta, Georgia. He is the son of Kathy and Randy Wittman and he has one sister, Lauren. Randy Wittman was formerly the head coach of the Washington Wizards and was previously head coach of the Cleveland Cavaliers (1999–2001) and Minnesota Timberwolves (2007–2008). The elder Wittman was a player on the 1980–81 Indiana Hoosiers men's basketball team which won a championship under Bob Knight. Drafted 22nd overall in the 1983 NBA Draft, Wittman played for NBA teams Atlanta Hawks, Sacramento Kings, and Indiana Pacers for nine seasons.
Ryan Wittman was born in Atlanta, when his father was a member of the Atlanta Hawks, but grew up in Eden Prairie, Minnesota and occasionally played pick-up games with Kevin Garnett at the Target Center. Wittman attended Eden Prairie High School, where he posted an average of 11.5 points per game in his junior year. He was named one of the preseason Top 30 players in Minnesota for the Class of 2006 by GopherIllustrated.com.
In July 2005, Wittman played for the AAU team Minnesota Select. The team was 5-1 in the Las Vegas Classic, an AAU playoff tournament. He led Select scorers with 15 points in a quarterfinal loss to the Houston Hoops, 59-53. Their season record was 27-14.
As a senior, his points per game average exploded to 20.5, and he hit 50 percent of his shots from three-point range and 84 percent from the foul line. One of the highlights of that season was upsetting Braham High School on December 30, 2005, who had a 65-game unbeaten streak snapped by the 80-67 loss to the Eagles. Wittman scored 30 points in that contest, including five-of-six from beyond the arc. After the season was over, Wittman was one of the five finalists for Minnesota Mr. Basketball and was listed as the sixth best Minnesota high school player by GopherIllustrated.com. In addition to being selected onto the First Team All Metro, he was a First Team All-State selection by the Timberwolves and a Second Team All-State selection by the St. Paul Pioneer Press.
He was recruited by Air Force, Bradley, Cornell, Eastern Kentucky, and Indiana. Cornell, which had recruited Wittman since his junior year in high school, was unable to offer him an athletic scholarship due to Ivy League rules. Nonetheless, Wittman inked his letter of intent to the Big Red on December 31, 2005.