Emery will imminently leave Villarreal after Aston Villa triggered a €6m release clause in his contract.
The 50-year-old will come in as a replacement for Steven Gerrard, who was sacked last week after a 3-0 defeat to Fulham.
Caretaker Aaron Danks was in charge when Villa trounced Brentford 4-0 over the weekend and he will once again be in the dugout against Newcastle United this weekend before Emery finally takes over.
Emery was previously in charge of Arsenal, where he lasted 18 months before being sacked but he has enjoyed success elsewhere, notably leading Sevilla to three Europa League titles and Villarreal to another triumph in Europe's secondary club competition.
'Aston Villa is delighted to announce the appointment of Unai Emery as the club's new Head Coach,' Villa said in a statement.
'Unai joins from Villarreal, whom he led to Europa League success by beating Manchester United in the final in 2021 as well as the semi-finals of the Champions League last season.
'A highly experienced top level coach who has managed over 900 games, Unai has also previously managed in the Premier League during a spell with Arsenal, leading the Gunners to a Europa League final.
'He has also enjoyed notable success at Sevilla and at Paris Saint Germain. In Seville, he won three successive Europa League titles between 2013 and 2016 before going on to lift a Ligue 1 championship in France as well as two French Cups, two French League Cups and two Trophée des Champions.
'Unai will take over from November 1st after his work permit formalities are completed.'
Emery's first game in charge of Villa will come against Manchester United in the Premier League.
