The two pop superstars will collaborate to choose the daily featured submission on the website.
Announcing the news on Wednesday (02Apr14), Madonna said, "There has never been a more crucial time to participate and help create change in the world. I’ve been so inspired by people’s submissions since we began and I welcome Miley’s input along with her fans to express themselves artistically and to share their creative ideas on the subject of human rights and freedom of speech.
"Miley and I look forward to hearing your voices in the format of your choice throughout the month of April and onward."
Thrilled Miley added, "I’m glad to join Madonna in encouraging people to have their voices heard at artforfreedom.com. It’s an ideal home to see how each of us can participate in changing the world for the better."
The singers will select a winning submission from all those tendered and present a $10,000 (Gbp6,250) grant to a charity of the winner's choice.
They last worked together when Madonna joined Miley for two songs at her MTV Unplugged show in Los Angeles in January (14). The two stars performed a mash-up of Miley's We Can't Stop and Madonna's Don't Tell Me while wearing matching glittery cowgirl outfits.
Madonna launched the Art for Freedom project in September (13). Katy Perry was the guest curator for the project in January (14).