Alex Kapp Horner is an American television actress and writer best recognized for her memorable supporting role on the popular CBS sitcom The New Adventures of Old Christine. Born Alexandra Kapp on December 5, 1969, in New York City, she embarked on a career in entertainment that would see her become a familiar face in numerous television comedies throughout the 2000s. Her professional name evolved over the years, from Alex Kapp to Alex Kapp Horner, and later back to Alex Kapp, reflecting her personal and marital journey.

Her early career consisted of guest appearances on various television series, building a foundation in the industry. She landed roles in shows like The Naked Truth, Caroline in the City, and The Drew Carey Show, often playing witty or sardonic characters that showcased her comedic timing. This period of steady work established her as a reliable presence in the ensemble casts of network sitcoms.

Kapp Horner's breakthrough came in 2006 when she was cast as Lindsay, the often-exasperated best friend and business partner of the title character played by Julia Louis-Dreyfus on The New Adventures of Old Christine. As a core member of the show's ensemble for its entire five-season run from 2006 to 2010, her performance contributed significantly to the series' critical acclaim, including an Emmy Award for Julia Louis-Dreyfus. This role remains her most prominent and defining work in television.

Beyond her most famous part, she continued to secure guest spots and recurring roles on other notable series. She appeared in episodes of How I Met Your Mother, Cougar Town, and The Exes, and had a multi-episode arc on Desperate Housewives. Her film work includes appearances in The Wedding Planner and The Third Wheel. In her personal life, she married Christian Horner, Vice President of Information Technology for Ticketmaster, in 1995. While her public acting appearances became less frequent following the conclusion of The New Adventures of Old Christine, her contribution to early 21st-century television comedy, particularly through her standout role as Lindsay, remains a significant part of her professional legacy.