Le Guen coached Cameroon at the 2010 World Cup and has agreed on a two-year deal, filling the void left after the sacking of LeRoy in January following the team's poor showing in the Gulf Cup and failure to qualify for the Asian Cup.
The former Paris St Germain, Olympique Lyon and Rangers coach will start work on 27 June as Oman build up for the first leg of their World Cup qualifier against either Mongolia or Myanmar on 23 July.
Le Guen was hired by former Rangers owner Sir David Murray in 2006 having coached Lyon to a hat-trick of French Ligue 1 titles but struggled at Ibrox, making the worst start to a season by a Rangers manager since John Greig in 1978-79.
Rangers were knocked out of the League Cup by St Johnstone, then in the First Division - the first time a lower league team had knocked Rangers out of a cup competition at Ibrox.
He stripped Barry Ferguson of the captaincy on 1 January 2007 and dropped him from the squad after a falling out, but, just three days later, it was announced Le Guen had left the club, becoming Rangers' shortest-serving manager.
He took over Paris St Germain later that month and saved them from relegation but struggled to re-establish the club to its former glories and, despite winning the League Cup in 2008, his contract was not renewed at the end of the 2008-09 season.
He was hired by Cameroon in July 2009 and led the team to South Africa in 2010, but they lost all three group games and were the first side knocked out.