United have reached an agreement on a deal worth an initial £42 million ($55.5m) with another £8m in potential add-ons. Ugarte is set to travel to Manchester on Tuesday to undergo a medical and formally complete the move.
The 23-year-old could make his debut against Liverpool at Old Trafford on Sunday, depending on international clearance.
The Uruguay international has been United’s top midfield target this summer and takes United’s spending during the transfer window to more than £180m.
The club are hoping to recoup a chunk of the money by allowing Scott McTominay to join Napoli. United have agreed a £25m fee with the Italian side and have given McTominay permission to discuss personal terms.
He made 37 appearances in all competitions for PSG last season after arriving from Sporting CP in a £50m move in 2023.
United are set to sanction more outgoings before Friday’s transfer deadline. Midfielder Hannibal Mejbri will join Championship side Burnley after undergoing a medical on Monday.
The club are also looking to offload defender Victor Lindelöf, although a move has been complicated by the Sweden international suffering a toe injury which has kept him on the sidelines.