On his racecourse debut Sovereign started at odds of 100/30 for a maiden race at Leopardstown Racecourse on 21 June and finished fifth, beaten seven and a halflengths by the Dermot Weld-trained winner Masaff. He was ridden in this race by Padraig Beggy a Ballydoyle work rider who had come to prominence in 2017 by winning the Epsom Derby on the 40/1 outsider Wings of Eagles. Two months later he was partnered by Michael Hussey in a similar event over one mile at the Curragh and came home sixth of the fourteen runners as victory went to his stablemate Mount Everest. On 18 September at Galway Races the colt started favourite for a maiden overeight and a halffurlongs on heavy ground in which he was ridden by his trainer's son Donnacha O'Brien. Sovereign took the lead soon after the start, went clear of his rivals approaching the last quarter mile and recorded his first success as he won "easily" by fourteen lengths despite being eased down by O'Brien in the closing stages. Twelve days after his win at Galway the colt was stepped up in class and started the 3/1 second choice in the betting behind Mount Everest in the Group 2 Beresford Stakes at Naas Racecourse. With O'Brien in the saddle he led for most of the way but was outpaced in the last two furlongs and came home fourth as the Ballydoyle third string Japan won narrowly from Mount Everest. He ended his season in the Group 3 Eyrefield Stakes at Leopardstown on 27 October in which he made the running before being overtaken in the final furlong and finishing third to Guaranteed and Masaff. In the official ratings for Irish-raced juveniles for 2018 Sovereign was given a mark of 103, making him 18 pounds inferior to the top-rated Quorto.
2019: three-year-old season
On his first two runs as a three-year-old Sovereign was partnered by Seamie Heffernan. He began his campaign in the Group 3 Ballysax Stakes over ten furlongs at Leopardstown on 27 April when he proved no match for his stablemate Broome and was beaten eight lengths into second place after briefly leading two furlongs out. In the Derrinstown Stud Derby Trial over the same course and distance two weeks later he kept on well in the straight without looking likely to win and finished third behind Broome and the Ballydoyle pacemaker Blenheim Palace. Sovereign was reunited with Beggy when he was one of seven O'Brien runners to contest the 2019 Epsom Derby and started a 50/1 outsider. Acting as a pacemaker for the stable's more highly-regarded contenders he went to the front and led the field into the straight before fading to come home tenth of the thirteen runners, just over nine lengths behind the winner Anthony Van Dyck. Sovereign was expected to fulfil a similar pacemaking role when he started at odds of 33/1 in an eight-runner field for the Irish Derby over one and a half miles at the Curragh on 29 June. Anthony Van Dyck started favourite ahead of Broome and the Epsom Derby runner-up Madhmoon while the other four runners were Rakan, Norway, Il Paradiso and Guaranteed. Beggy sent the colt to the front soon after the start, opened up a clear advantage at half way and increased his lead entering the straight. He never looked in the slightest danger of defeat in the closing stages and won "easily" by six lengths from Anthony Van Dyck. Aidan O'Brien commented "Padraig was in front and he was comfortable and his horse kept coming. I'd say anytime that you make the running you have to get the fractions right, and he did. The Curragh is a big, open galloping track and he has a massive stride. The undulations at Epsom might not have suited him as much". He went on to mention the Grand Prix de Paris, King George VI & Queen Elizabeth Stakes and St Leger as possible future targets. In September Aidan O'Brien announced that Sovereign would not race again in 2019, saying "He hasn't had a setback, we just want to give him time".
