Isabelle Mercier (born August 5, 1975 in Victoriaville, Quebec) is a professional poker player.

Mercier originally learned to play poker as a child, but prior to turning to a poker career, she earned an undergraduate law degree from the Université de Montréal and practiced commercial law for six months. She then moved to Paris, France and earned a master's degree while working as the poker room manager at the Aviation Club de France, before turning to poker full-time. During her time working at the Aviation Club she was nominated for Staff Person of the Year twice at the European Poker Awards.

She first made a name for herself by finishing in second place in the €800 No Limit hold 'em tournament at the Masters Classic of Poker 2002 in Amsterdam, where she earned $53,499.

In 2004 Mercier won the World Poker Tour (WPT) Ladies' Night tournament and the $25,000 first prize, where Mike Sexton nicknamed her "No Mercy."

In 2005 she finished tenth in the European Poker Tour (EPT) Grand Final in Monte Carlo, earning €23,090, and outlasting players such as World Series of Poker (WSOP) runner-up Julian Gardner, WPT multi-tournament winner Gus Hansen, WPT season 2 champion Martin De Knijff and Barny Boatman. Also in 2005, she had three money finishes at the WSOP.

Mercier made her first EPT final table in February 2006 in Deauville, finishing seventh at a final table also featuring Ram Vaswani and Kirill Gerasimov.

Mercier has her own instructional DVD and appeared in the documentary That's Poker. In January 2008, she released her own biography: Profession : bluffeuse (Profession: Bluffer), in Montreal and printed in France by Flammarion.

Until 2009, she was a member of the PokerStars online poker cardroom's "Team PokerStars" group of sponsored players.

On April 27, 2009, Mercier won the PokerStars' Ante Up for Africa charity tournament in Monte Carlo. The final table included fellow Canadian Daniel Negreanu, Australian Tony G, John Duthie (creator of the European Poker Tour), Italian pro Dario Minieri (who finished third), and English soccer star Teddy Sheringham (who came in second).

On July 12, 2009, Mercier finished 3rd in the PokerStars Sunday Millions, cashing for $115,000, her second highest cash to date.

By the end of 2009, Mercier left the PokerStars pro team and on December 2, 2009, joined gambling giant BetClic as a consultant for their online poker site.

Mercier's total live tournament winnings exceeded $1,200,000 as of 2015.