Henrikh Mkhitaryan will have a medical at Manchester United in the next week as Borussia Dortmund have accepted a £26.3m bid for the Armenian midfielder.
The 27-year-old had an outstanding season, winning the Bundesliga player of the season, scoring 23 goals and making 32 assists in all competitions.
Mkhitaryan is also Armenia's all-time top goalscorer, scoring 19 goals in 59 games for his national side.
The Armenia captain is set to be one of a number of high-profile signings for Manchester United as Mourinho is also targeting veteran striker Zlatan Ibrahimovic.