Susan Egan was born on February 18, 1970, in California. Before pursuing a professional performing career, she trained as a child in dance, singing, and ballet, and was a competitive figure skater from ages five to ten. After studying at the University of California, Los Angeles, she left to accept a touring role and soon after originated the role of Belle in the Broadway musical adaptation of Beauty and the Beast, a performance that earned her a Tony Award nomination.

While Egan is highly regarded for her stage and musical theater work, she is also an accomplished voice actor with several notable roles in English dubs of Japanese anime. She provided the English voice for Madame Gina in the Studio Ghibli film Porco Rosso. This character is a sultry lounge singer and the owner of the Hotel Adriano, who shares a deep, complicated history with the titular pig-headed pilot. In another celebrated anime film from the same studio, Egan voiced Lin in the English dub of Spirited Away, a tough but kind-hearted worker in the boiler room of the bathhouse.

Her work in English dubs represents a smaller portion of a larger voice acting career that includes prominent roles in American animation. She is widely recognized for voicing Megara in the Disney film Hercules and later reprised the role in the animated series and video game sequels such as Kingdom Hearts III. Another significant role was providing the voice for Rose Quartz, also known as Pink Diamond, on the Cartoon Network series Steven Universe. Her other voice credits include the singing voice of Angel in Lady and the Tramp II: Scamp's Adventure, as well as guest roles on animated series like Amphibia and The Simpsons.