Thunder Moon is a bay colt with a white star and snip bred in Ireland by Whisperview Trading a breeding company owned by Aidan O'Brien and his wife Anne Marie.

[3] Thunder Moon's dam Small Sacrifice never appeared on a racecourse but was a granddaughter of the successful racehorse and broodmare Trusted Partner, whose other descendants have included Search For A Song and Free Eagle.

On 13 September Thunder Moon was moved up sharply in class to contest the Group 1 National Stakes at the Curragh in which he was again partnered by McDonogh.

After racing in mid-division he made steady progress in the closing stages but was beaten into third place behind St Mark's Basilica and Wembley, finishing two and a half lengths behind the winner.

[8] In the official European classification of for 2020 Thunder Moon was given a rating of 117, making him the fourth best two-year-old of the season three pounds behind the top-rated St Mark's Basilica.