"In the first place, I thank AS Monaco for giving me the opportunity to coach the team of this club so special to me".
The 41-year-old French World Cup victor, who had been working as an assistant to Belgium coach Roberto Martinez since 2016, returns to the club where he began his professional career.
The Frenchman was confirmed as Leonardo Jardim's replacement on Saturday morning after days of negotiations with his former club.
"The first season was very complicated", he said, wishing Henry "lots of courage and big success".
Henry also played for Barcelona and New York Red Bulls during the course of his career.
"Monaco will always be close to my heart".
Indeed, Henry's task is a hard one as he is charged with turning around the form of a side which have picked up only six points from nine Ligue 1 matches this season.
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Jardim was relieved of his duties after Monaco slipped to 18th in the Ligue 1 standings before the worldwide break.
However, his resources could have been even more enviable had Monaco not sold so many of their top players in recent years. He won seven trophies with the Gunners, among them two Premier Leagues, including the unbeaten 2003-04 side.
He was part of the staff that led the team to 3rd place at the World Cup in Russian Federation.
Henry began his senior playing career with Monaco in 1994, during which time he played under future Arsenal manager Arsene Wenger. He scored at least 20 league goals in six consecutive seasons and became Arsenal's all-time leading goalscorer.
Henry was a World Cup victor with France in 1998 and won the European Championship two years later, scoring 51 goals in 123 appearances for Les Bleus.
Henry had worked alongside former Everton boss Roberto Martinez in the Belgium set-up, and helped the side to a third-placed finish at the World Cup in Russian Federation.