'Pokémon' Star Rachael Lillis Dead After Breast Cancer Battle

Rachael Lillis, the voice actor best known for voicing Misty, Jessie and Jigglypuff in the "Pokémon" franchise, has died ... her sister, Laurie Orr, confirmed.

The veteran performer passed away peacefully in her sleep Saturday evening ... after battling breast cancer. Laurie -- who shared the news on the GoFundMe launched for her sister's care -- said she was unable to be by Rachael's side when she passed, but assured fans RL died "without pain."

She added ... "It was just this past week that she was starting to decline. This was unexpected and we are completely grief-stricken. We ask for peace, for now, as her family grieves this loss."

Rachael's "Pokémon" costar Veronica Taylor -- who notably voiced Ash Ketchum in the popular cartoon -- took to Instagram Monday to pay tribute to the late star.

In a poignant message to fans, Veronica shared how their love and support helped Rachael throughout her cancer battle.

She continued ... "I was lucky enough to know Rachael as a friend. She had unlimited kindness and compassion, even until the very end."

In addition to her work in the "Pokémon" franchise, Rachael was a staple in the anime community, having voiced characters in several films and TV shows ... including "Hunter × Hunter: The Last Mission," "Berserk: The Golden Age Arc," "Sonic X," "Animation Runner Kuromi," and "Guardian of Darkness."

She was 46 years old.