Orozco, 18, joins from Fortaleza CEIF having agreed to the move as a minor last October, only completing the switch to Old Trafford after turning 18 on 13 July under FIFA's rules on transfers involving under-18 players.
The midfielder, who progressed through Rojo FC's academy before his move to Fortaleza, made five senior appearances in the Categoría Primera A last season and captained Colombia to the Under-17 World Cup in Qatar. He becomes only the second Colombian to represent Manchester United after Radamel Falcao and will initially train and play with the Academy as he settles into life in Manchester.
At the other end of the squad, United have told at least three senior academy players they are free to leave permanently this summer, with the club open to loan offers for much of the rest of its Under-21 squad. Midfielders Dan Gore and Toby Collyer, along with left-back Harry Amass, are among those facing an exit, while only a handful of prospects - including Shea Lacey, Jack and Tyler Fletcher, and 15-year-old JJ Gabriel - are considered untouchable.
Amass, 19, is expected to be sold for around £6m, with several Championship clubs interested; United have let his contract, signed in 2023, run down towards its 2027 expiry rather than offer fresh terms.
Gore, 21, impressed across two loan spells at Rotherham United despite the club's relegation from League One, but has made just a single senior United appearance, in the League Cup against Crystal Palace in September 2023. He and Collyer were both left out of the squad that beat Atletico Madrid 2-1 in a pre-season friendly in Stockholm, with Gore instead captaining United's Under-21s to a 1-0 defeat by non-league Altrincham.
Newly promoted Hull City, where Collyer spent an injury-hit loan spell last season, are among the clubs interested in re-signing the 22-year-old. Elsewhere, midfielder Jacob Devaney could also depart on loan, while striker Chido Obi's future remains unresolved - the striker is open to a temporary move away from Old Trafford, but only if it guarantees him regular first-team football.