Alexandra Maria Guarnaschelli (born June 20, 1969) is an American chef, cookbook author, and television personality. She currently serves as an executive chef at New York City's Butter restaurant and was executive chef at The Darby restaurant before its closing. Guarnaschelli studied cooking extensively in France.

She appears as a television personality on the Food Network shows The Kitchen, Chopped (as a judge), Iron Chef America, All Star Family Cook-off, Guy's Grocery Games (as both a judge and a competitor), and The Best Thing I Ever Ate. She hosts Alex's Day Off, The Cooking Loft, and Supermarket Stakeout. In 2012, she won that season of The Next Iron Chef: Redemption. In January 2022, she premiered her newest show, Alex vs. America, also on Food Network.

In 2013, Guarnaschelli's first cookbook was published. Old-School Comfort Food: The Way I Learned to Cook mixes autobiographical details with favorite recipes from her professional life that she adapted for the home.

Guarnaschelli was the only child of cookbook editor, the late Maria Guarnaschelli and John Guarnaschelli. She was born in St. Louis, Missouri, but the family moved to New York City when she was just a few days old.

Guarnaschelli's culinary experience started while watching her mother test numerous recipes at home while editing cookbooks.

She graduated from Horace Mann School in 1987 and from Barnard College in 1991 with a degree in art history.

In 1991, she worked for minimum wage in a restaurant, An American Place, for one year.^{[citation needed]}

Guarnaschelli worked under Larry Forgione (whose son is Iron Chef Marc Forgione), and then at a number of restaurants in France, New York and Los Angeles, including Guy Savoy's La Butte Chaillot. She also worked at Daniel Boulud's eponymous restaurant and Joachim Splichal's Patina, before becoming the executive chef at Butter Midtown in 2003. She was executive chef at The Darby restaurant before its closing in 2013. She chairs the Museum of Food and Drink's Culinary Council.