After several weeks of vignettes, Angle made his in-ring debut on November 14, 1999 at the Survivor Series at the Joe Louis Arena in Detroit, Michigan, defeating Shawn Stasiak. In his initial push, he remained undefeated for several weeks, eventually losing to the debuting Tazz at the Royal Rumble. Angle's television character was an "American hero" gimmick based on his gold medal win at the 1996 Summer Olympics. In his promos, Angle presented himself as a role model and stressed the need to work hard to realize one's dreams, stressing the 3 I's, "Intensity, Integrity, and Intelligence". In his promos and ring entrances, Angle would always wear replicas of his gold medals around his neck. While he stood for many principles that are associated with "good guy" wrestlers, Angle's character put an arrogant spin on them to act as a villain, talking down to the audience and behaving as if he thought he was better than the fans. Angle won both the European Championship and the Intercontinental Championship in February 2000, billing himself as the "Eurocontinental Champion". He dropped both of his titles without ever conceding a fall in a two falls Triple Threat match with Chris Benoit and Chris Jericho at WrestleMania 2000. The match had been agreed to on Angle's behalf by his mentor, Bob Backlund.
Throughout mid-2000, Angle and ("Team ECK" (Edge, Christian and Kurt)) feuded with Too Cool and Rikishi, with Angle defeating Rikishi in the finals of the King of the Ring tournament. He went on to feud with Triple H after a love triangle between Angle, Triple H, and Triple H's wife Stephanie McMahon developed. As a change to the intended storyline of Stephanie turning on her husband and going with Angle, he lost to Triple H at Unforgiven. Following his feud with Triple H, Angle received another push and began pursuing the WWF Championship, defeating The Rock at No Mercy, after botched interference on The Rock's behalf from Rikishi. With his victory over the Rock, Angle became the first wrestler to have won both an Olympic Gold medal and the World title. Angle retained the WWF Championship for the rest of the year in matches with The Undertaker at Survivor Series and in a six way Hell in a Cell match at Armageddon.
After beating Triple H at the Royal Rumble, Angle eventually lost the title to The Rock at No Way Out, after holding the WWF Championship for four months. He then feuded with Chris Benoit, whom he defeated at WrestleMania X-Seven but lost to him at Backlash in an Ultimate Submission match; Benoit defeated Angle four falls to three in sudden-death overtime. Continuing the feud, Angle again defeated Benoit in a two out of three falls match at Judgment Day. Benoit pinned Angle after an Angle Slam in a "Pinfalls Only" fall, and then Angle made Benoit submit with the ankle lock in the "Submissions Only" fall. Angle won the third fall, a Ladder match, with the help of Edge and Christian.
When invading superstars and ECW formed The Alliance and invaded the WWF in mid-2001 (dubbed as "The Invasion"), Angle became a fan favorite and began a storyline where he joined forces with WWF Champion Steve Austin to repel them. At Invasion, Angle and Austin captained a team of five WWF superstars against five handpicked members of the Alliance. As part of the angle, Team WWF lost to Team Alliance when Austin turned on his team to join The Alliance. At the close of the match, Austin nailed Angle with a Stone Cold Stunner, causing him to get pinned by the other team. After winning and losing the United States Championship, and the WWF Hardcore Championship in matches with Alliance members, Angle was booked to defeat Austin in a SummerSlam rematch for his second WWF Championship at Unforgiven. He dropped the title back to Austin on the October 8, 2001 episode of Raw when WWF Commissioner William Regal joined The Alliance and cost Angle the match. As part of the storyline, Angle subsequently turned into a villain again and joined the Alliance himself; during a WrestleMania X-Seven rematch between Vince McMahon and Shane McMahon, he interfered seemingly to aid Vince but instead struck the members of team WWF with a steel chair. Angle, however, ultimately returned to the WWF side by enabling The Rock to defeat Austin in a "Winner Takes All" match between the WWF and The Alliance at Survivor Series. He remained a villain by claiming sole responsibility for the destruction of The Alliance.
After dropping the United States Championship to Edge, the duo were booked into a lengthy feud. During this feud, Edge helped the fans with the already started "you suck" chants every time Angle entered a WWE ring, usually in tune with Angle's entrance music. The chants followed Angle throughout the rest of his WWE career. In the course of the feud, the naturally balding Angle lost a "hair versus hair" match to Edge at Judgment Day, and his head was shaved bald. Following the loss of his hair, Angle's storyline called for him to wear a wig and insult bald people, leading to a feud with Hollywood Hogan, who stripped Angle of his wig. Angle later scored a submission victory over Hogan at King of the Ring. In 2002 Kurt wrestled John Cena in Cena's first ever WWE match. Kurt went on to win the match by a roll up pin.
In October 2002, Angle became the fifth WWE Grand Slam Championship winner when he won the WWE Tag Team Championship with Chris Benoit at No Mercy 2002. Their team was successful but problematic, as the two bickered constantly, with Benoit often fed up with Angle's over-the-top antics. After dropping the title to Edge and Rey Mysterio on an episode of SmackDown!, Angle won his third WWE Championship at Armageddon, defeating The Big Show, with the help of Brock Lesnar. While still in his third reign, Angle began a new storyline when he gained the services of manager Paul Heyman and "Team Angle".
He then began feuding with Brock Lesnar, who had won the 2003 Royal Rumble match, after Lesnar claimed to be the new top superstar on SmackDown!. Angle dropped the WWE Championship in the main event of WrestleMania XIX to Lesnar.
On April 11, 2003, Angle underwent neck surgery performed by Dr. Hae-Dong Jho to repair nerve and spinal damage, calcium buildup, bone spurs, and intervertebral disc problems. He returned as a face character in June. Shortly after returning, Angle defeated Lesnar and Big Show in a Triple Threat match at Vengeance to regain the WWE Championship. During this time, Lesnar seemed to become an ally to Angle. Lesnar, however, secretly worked with Vince McMahon on a plot against Angle, turning on him during a steel cage match between himself and McMahon in which Angle was the special guest referee, and stated that he never tolerated losing the belt to him at Vengeance. After retaining the title in a singles bout at SummerSlam by making Brock Lesnar tap out to the ankle lock, he dropped the title to Lesnar in an Iron Man match on an episode of SmackDown!. Angle then formed a five-man team to rival Lesnar's team at the Survivor Series, with Angle's team coming out victorious.
Angle then got involved in a feud with Eddie Guerrero. Initially being a firm friend and ally to Eddie during the latter's feud with his nephew Chavo, Angle turned on him when it was announced that Guerrero, not Angle, was the number one contender for the WWE Championship, thus becoming a villain once again. At No Way Out, Guerrero defeated Lesnar to win the WWE Championship, and Angle won a match to become new number one contender. After losing to Guerrero at WrestleMania XX, Angle began to once again suffer from legitimate neck problems. As a response, he was made the on-screen General Manager of SmackDown!, with his absence from the ring attributed to injuries suffered after Big Show chokeslammed him off a ledge. Angle continued his feud with Guerrero throughout 2004. He cost Guerrero the WWE championship against John "Bradshaw" Layfield in a Texas Bull Rope match at The Great American Bash by participating in the worked finish; Angle came down to the ring and showed a replay where JBL's shoulder hit the corner pad before Guerrero's hand. Angle was later fired by Vince McMahon as General Manager in July 2004, after discovering that he was faking his handicapped status.
In November 2004, Angle initiated the Kurt Angle Invitational, a worked weekly segment where "hometown heroes" (plants), challenged him to a match, with Angle promising to give his Olympic gold medal to the first person to last more than three minutes in the ring with him. The Invitational was won by Eugene in July 2005 starting a new angle for both men. As a result, Angle faced Eugene at SummerSlam, defeating him by making him tap out to the ankle lock.
On November 4, 2004, episode of SmackDown!, taped in St. Louis, Missouri, during an unscripted segment of Tough Enough, Angle challenged the finalists through a squat thrust competition. Chris Nawrocki won the competition, and the prize Nawrocki won was a match against Angle. Angle quickly took Nawrocki down, breaking his ribs, then made him tap out with a neck crank. After Angle defeated Nawrocki, Angle challenged the other finalists. Daniel Puder, an American professional mixed martial artist, accepted Angle's challenge. Angle and Puder wrestled for position, with Angle taking Puder down, however, in the process, Puder locked Angle in a kimura lock. With Puder on his back and Angle's arm locked in the kimura, Angle attempted a pin, one of two referees in the ring, Jim Korderas, quickly counted three to end the bout, despite the fact that Puder's shoulders weren't fully down on the mat, bridging up at two.
In January 2005, Angle took part in the Royal Rumble, but was eliminated by Shawn Michaels, who had returned to the ring to eliminate in retaliation. After mocking Michaels by defeating his former tag team partner, Marty Jannetty, and attacking former manager, Sherri Martel, Angle defeated Michaels in an interpromotional match at WrestleMania 21. He continued to feud with Michaels upon being drafted from SmackDown! to Raw in the 2005 WWE Draft Lottery, losing to Michaels at Vengeance. Angle later challenged John Cena for the WWE Championship at Unforgiven, where Angle won the match by disqualification, thus not winning the title. Angle also challenged Cena again in a Triple Threat match along with Michaels at Taboo Tuesday, in a losing effort.
Angle returned to the SmackDown! brand in January 2006, where he was pushed to gain the vacant World Heavyweight Championship in a twenty man battle royal, turning face in the process for the first time since 2004. He retained the title against Mark Henry at the Royal Rumble. Shortly after the match, The Undertaker made his return and challenged Angle for the title. Angle retained the title in a match with Undertaker at No Way Out before indirectly dropping it to Rey Mysterio in a Triple Threat match, which also included Randy Orton, at WrestleMania 22.
On May 29, 2006, Angle was drafted to the newly created ECW brand. It was during this time that he acquired the nickname "The Wrestling Machine," wearing a mouth guard and quickly squashing opponents. Upon coming to ECW, he issued an open challenge for One Night Stand, which was accepted by Orton. Angle defeated Orton at One Night Stand, later losing to him in a rematch at Vengeance. Angle appeared sporadically on WWE television throughout mid-2006. On August 25, 2006, Angle was granted an early release from his WWE contract because of health reasons.