On December 26, Griffin was named to enter the 2013 Pro Bowl in recognition of his successful rookie season. Due to injuries on his ACL and LCL ligaments in his right knee, he was negated from the Pro Bowl roster and replaced by Drew Brees. Griffin also won the 2012 NFL Offensive Rookie of the Year award. He was named to the PFWA All-Rookie Team, becoming the second Redskins quarterback to receive this award, joining Heath Shuler in 1994.

Griffin was born in Okinawa, Japan, where his parents, Robert Jr. and Jacqueline, both U.S. Army sergeants, were stationed. The family later lived at Fort Lewis near Tacoma, Washington, and then moved to New Orleans, Louisiana. They finally settled in Copperas Cove, Texas in 1997 after retiring from the military.

In track, Griffin broke state records for the 110-meter and 300-meter hurdles. He ran the 110-meter hurdles in 13.55 seconds and the 300-meter hurdles in 35.33 seconds. The 300 hurdles time was 1/100th of a second short of tying the national high school record at the time. He was also a gold medalist in the 110- and 400-meter hurdles on the AAU track and field circuit. In 2007, as a junior, he was rated the No. 1 high school 400-meter intermediate hurdler in the country, and was tied at No. 1 for the 110-meter sprint hurdler in the nation. His personal best in the 110-meter hurdles, 13.46 sec, ranked fifth in the world among junior athletes in 2007 (behind Noga, Brathwaite, Dutch, and Vladimir Zhukov), while his best 2007 time in the 400-meter hurdles, 49.56 sec—his personal best until 2008—led all juniors worldwide for that year. Also as a junior, Griffin received the Gatorade Texas Boys Track and Field Athlete of the Year award, and was named to USA Today′s 2007 All-USA Track and Field team. His personal best in the 400-meter hurdles was achieved on May 18, 2008, with a time of 49.22 seconds.

Coming into the 2011 season, the Baylor Bears were not expected to do well, being picked 6th in the Big 12 preseason poll. The Bears opened the season against 15th-ranked TCU. The Bears took a 47–23 lead into the 4th quarter, and were able to fight off a comeback after the Horned Frogs gained the lead 48–47 briefly, only for Baylor to kick the game-winning field goal and win 50–48. They pulled off the upset in large part due to Griffin’s performance; he passed for 359 yards, with 5 touchdowns and a 77.8% completion percentage. On the game-winning drive, Griffin also caught a key pass. Following the win, Baylor entered the AP Poll rankings for only the third time in the previous 15 seasons, at 20th, and Griffin was considered by many to be a Heisman Trophy candidate. After a bye week, Baylor shut out Stephen F. Austin State University 48–0, and Griffin went 20 of 22 (90.9%) for 247 yards and 3 touchdowns and ran for 78 yards. In week 4, Griffin ushered Baylor to their third win, beating Rice University 56–31; Griffin completed 29 of 33 passes (87.9%) for 338 yards with 51 yards rushing and a touchdown. In week five against Kansas State, Griffin almost brought the Bears to their fourth win, going 23 out of 31 (74.2%) for 346 yards and 5 touchdowns with only 1 interception, but they lost 36–35 to the Wildcats. In week six against Iowa State, Griffin took Baylor to Iowa for their fourth win, completing 22 out of 30 (73.3%) for 212 yards, 1 touchdown, and no interceptions. He won the Heisman Trophy, becoming the first player from Baylor to win it. Griffin also led Baylor to a 10–3 record, including a 67–56 win over the Washington Huskies in the Alamo Bowl. With a combined 123 points, it stands as the highest-scoring regulation bowl game in NCAA history. Due to the Alamo Bowl, Griffin became the first player since Tim Tebow in 2007 to win the Heisman and not appear in the National Championship (#1 LSU faced #2 Alabama). Overall, he finished the 2011 season with 4,293 passing yards, 37 passing touchdowns, and six interceptions to go along with 179 rushes for 699 rushing yards and ten rushing touchdowns.

Griffin began dating fellow Baylor student Rebecca Liddicoat in 2009, and the two were married on July 6, 2013. Rebecca gave birth to Griffin’s first child, a daughter in 2015. On August 16, 2016, it was reported that Griffin and his wife were separated and in the process of filing for divorce.

Griffin, who graduated with a Bachelor of Arts degree in political science with a 3.67 grade point average in December 2010, began pursuing a Master’s in communications in 2011. On January 11, 2012, Griffin officially announced his intention to enter the 2012 NFL Draft.

Griffin was widely projected to be the No. 2 pick of the draft, but the St. Louis Rams—the team originally holding the pick—had already selected Sam Bradford to be their long-term starting quarterback with the No. 1 overall pick in the 2010 NFL Draft. Wanting to stick with Bradford, the Rams decided to deal the pick prior to the draft, with the Cleveland Browns and Washington Redskins perceived as the most interested bidders. After a brief bidding process, the Redskins acquired the pick by giving the Rams four high-value draft picks over three years: their first-round picks in 2012 (No.6 overall), 2013 (No.22 overall), and 2014 (No.2 overall), as well as their second-round pick (No.39 overall) in 2012.

Griffin wore number 10 for the Redskins, with “Griffin III” on the back of his jersey. This made him the first player in the history of the “Big Four” professional sports leagues (NFL, MLB, NHL, and NBA) to have a Roman numeral on the back of his jersey, as the NFL changed the rule in 2012 to allow players to include generational titles in their names. Griffin previously had “Griffin III” on the back of his jersey while in college, which was actually necessary in order to distinguish him from the other Robert Griffin on the Baylor team. On July 18, 2012, the Redskins officially signed him to a four-year, $21.1 million contract with a $13.8 million signing bonus.

On September 9, 2012, Griffin officially became the NFL’s first starting quarterback who was born in the 1990s. In his official debut as a starting quarterback in the NFL, Griffin opened the Redskins’ season by completing 19 of 26 passes for 320 yards and 2 touchdowns while adding 10 carries for 42 rushing yards in a 40–32 victory over the New Orleans Saints. He was named NFC Offensive Player of the Week for his performance – the first time in NFL history that a rookie quarterback has been given that honor for his debut game. Griffin’s debut performance was further rewarded after he was named NFL Rookie of the Week, and he was given that honor once again after the Redskins’ win over the Tampa Bay Buccaneers in Week 4. On October 4, he was named September’s NFL Offensive Rookie of the Month. The next week against the Atlanta Falcons, he left the game late in the third quarter after suffering a mild concussion after receiving a blow to the head by Sean Weatherspoon. He was cleared to play in the next game against the Minnesota Vikings, where he had another impressive performance that included a 76-yard rushing touchdown. The Redskins ended their home-game losing streak and Griffin was named NFL Rookie of the Week for a third time.

On September 14, 2014, in Week 2, against the Jacksonville Jaguars, Griffin was carted off the field after suffering a dislocated left ankle. X-rays and MRIs revealed no fractures in the ankle. On October 29, it was reported that Griffin was set to return against the Minnesota Vikings in week 9. The Redskins then dropped their next three games, falling to the Vikings, Buccaneers, and 49ers. On November 25, it was reported that Griffin would be benched for Colt McCoy, heading into Sunday’s game against the Indianapolis Colts. After McCoy went down with a neck injury against the New York Giants, Griffin came in and looked impressive in a loss to the Giants, throwing for 236 yards and 1 touchdown passing. Griffin was named the starter for the rest of the year when the Redskins put Colt McCoy on injured reserve. Griffin responded to that with a winning performance in a 27–24 victory over the Eagles. He threw for 220 yards and had one interception. In the final game of the year against the Cowboys, Griffin showed strides of his rookie year. He threw for a season-high 336 yards and had 2 touchdowns (one passing, one rushing) in a 44–17 loss. Griffin was 2–5 as a starter in 2014 and the Redskins finished 4–12 and last place in the NFC East.

On September 13, 2015, it was reported that Griffin was practicing as a safety with the scout team. He ended up third on the quarterback depth chart, behind Cousins and Colt McCoy, and remained inactive for the entire regular season.

On March 7, 2016, Griffin was released by the Redskins.

On March 24, 2016, Griffin signed a two-year, $15 million contract with the Cleveland Browns. On August 8, 2016, Browns head coach Hue Jackson named Griffin the team’s starting quarterback for the 2016 season. Griffin was placed on injured reserve on September 12, after suffering a shoulder injury in the Browns’ season opening loss to the Philadelphia Eagles. He was activated off injured reserve on December 9, 2016, prior to Week 14 against the Bengals. Griffin played in five games, all starts, in 2016, completing 87-of-147 passes for 886 yards with two touchdowns and three interceptions. He also rushed for 190 yards and two touchdowns.

In August 2016, Griffin and Estonian heptathlete Grete Šadeiko became romantically linked. They were engaged on May 13, 2017. In 2017, Griffin announced via Instagram the birth of his second daughter. The couple married on March 10, 2018. His third daughter was born in September 2019.

On March 10, 2017, Griffin was released by the Browns.

After remaining a free agent for all of 2017, Griffin signed a one-year contract with the Baltimore Ravens on April 4, 2018. On September 2, 2018, Griffin was named the team’s backup quarterback. Backing up Joe Flacco and Lamar Jackson, Griffin appeared in three games in the 2018 season.

On March 21, 2019, Griffin re-signed with the Ravens on a two-year contract. On July 28, 2019, Griffin suffered a fractured thumb and was expected to miss 4–8 weeks. Griffin returned in time for the September 8, 2019 regular season opener against the Miami Dolphins, where Griffin came into the game in relief of Lamar Jackson toward the end of the 59–10 victory. He completed all six pass attempts for 55 yards and one touchdown. In the Week 10 game against the Cincinnati Bengals, Griffin entered the game as a running back alongside Mark Ingram Jr. and Jackson in the backfield, marking what was likely the first time in NFL history three former Heisman Trophy winners lined up together in a backfield. In Week 17 against the Pittsburgh Steelers, Griffin made his first start since the 2016 season because the Ravens secured the top seed in the AFC playoffs and sat their starters as a result. During the game, Griffin threw for 96 yards and an interception and rushed for 50 yards during the 28–10 win.