James McDonald will ride Trustyourinstinct in the Melbourne Cup on November 3.
The Cup runs over 3200 metres at Flemington Racecourse in Melbourne.
Trainer Joseph O'Brien held off naming a rider until after the Cox Plate on Saturday.
Aeliana placed third in the Cox Plate but is all but certain not to run in the Cup.
Trustyourinstinct has nine wins from 25 starts, including the Curragh Cup this year.
He finished fourth in the Group 1 Irish St Leger against top horses.
O'Brien won the Cup with Rekindling in 2017 and Twilight Payment in 2020.
Trustyourinstinct is one of five O'Brien-trained runners in the Cup mix.
Craig Williams rides James J Braddock, while Ryan Moore rides Sons And Lovers.
Cox Plate winner William Pike will ride Cignetti in the Victoria Derby on Saturday.
Pike will ride Zakouma in the Melbourne Cup on November 3.
Third acceptances close at 10am on Monday, October 26, before the final field is set.
Get the full breakdown, key numbers, and what happens next.
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