For the 2020 season Mare Australis moved into the ownership of Corinna Baronin Von Ullmann and was transferred to the stable of André Fabre at Chantilly in France.
[6] On his first appearance for his new connections Mare Australis started favourite for the Prix Tourbillon over 2100 metres at Saint-Cloud Racecourse on 12 May but finished fourth behind Port Guillaume, Gold Trip and Dawn Intello, beaten three lengths by the winner.
On 14 June the colt was moved up in class and distance for the Listed Prix de l'Avre over 2400 metres at Chantilly Racecourse in which he was ridden, as in all of his 2020 starts, by Pierre-Charles Boudot.
[7] On his only subsequent start Mare Australis contested the Group 2 Prix du Conseil de Paris on heavy ground at Longchamp Racecourse on 25 October.
Boudot sent Mare Australis into the lead from the start and he was never seriously challenged, winning by one and three quarter lengths from Gold Trip despite being eased down in the closing stages.