France Under-19 defender Steven Moreira has signed his first professional contract with Ligue 1 club Rennes.
Montpellier coach Jean Fernandez has resigned after overseeing a run of seven Ligue 1 games without victory.
The 18-year-old full-back, a product of Rovers' academy, will remain at Ewood Park until June 2017, with the option of a further year.
"It is fantastic, it is something I've been working towards for a long time now and it feels great to get it done," Henley told the club's official website
"I really enjoy it here, I always have, I've been here since I was nine or 10 and I've enjoyed every minute of it. It feels great to secure my time here."
Henley made his first-team debut as a second-half substitute away to Wigan
last November, and his full Premier League debut came just a month later in the Boxing Day draw at Liverpool.