In Jacques Audiard's drama Rust and Bone (De rouille et d'os), alongside Matthias Schoenaerts, Cotillard portrayed the orca trainer Stéphanie, who loses her legs after an accident at work and begins a strange relationship with Schoenaerts' character. The film premiered at the 2012 Cannes Film Festival and received a ten-minute standing ovation at the end of its screening. Cotillard garnered rave reviews for her performance, and Cate Blanchett wrote an op-ed for Variety praising her, describing the film as "simply astonishing" and stating that "Marion has created a character of nobility and candour, seamlessly melding herself into a world we could not have known without her. Her performance is as unexpected and as unsentimental and raw as the film itself". She received a fifth César Award nomination, a fourth Screen Actors Guild Award nomination, a third Golden Globe nomination (her first nomination for Best Actress – Drama), a second Critics' Choice Award nomination and a second Lumières Award nomination. Cotillard also received several honours and career tributes in 2012, at the Telluride Film Festival, Hollywood Film Festival, AFI Fest, Gotham Awards and Harper's Bazaar Awards.
Cotillard recorded the song "The Eyes of Mars" with Franz Ferdinand especially for Dior. In 2012, she wrote and performed the song "Lily's Body" for the fourth episode of the Lady Dior Web Documentary with the same title, and in 2014, Cotillard wrote and performed the song "Snapshot in LA" alongside John Cameron Mitchell, Metronomy's Joseph Mount and Villaine. She also wrote and co-directed the video for the song, made for Lady Dior's advertising campaign "Enter the Game – Dior Cruise 2015".
In 2012, Cotillard was featured on Kate Winslet's book "The Golden Hat: Talking Back To Autism", with celebrity self-portraits to raise awareness and support for autism launched by Winslet's Golden Hat Foundation. In 2013, she caged herself near Paris's Louvre museum to demand the freeing of 30 Greenpeace activists jailed in Russia over an Arctic protest. She entered the cage and held a banner proclaiming "I am a climate defender".
In 2012, Cotillard starred in the web-series Lady Dior Web Documentary and wrote and performed the song "Lily's body" for one episode, she also designed her own handbag for Dior, the "360° bag". Cotillard also appeared on the cover of the first issue of Dior Magazine in September 2012. In 2014, she wrote and co-directed alongside Eliott Bliss, a music video for her song "Snapshot in LA", especially for Lady Dior's campaign "Enter The Game – Dior Cuise 2015".
In 2012, Cotillard was named "The World's Sexiest Woman" by the Hungarian magazine Periodika. In 2013, she was ranked No. 13 on Empire Online's list of the "100 Sexiest Movie Stars", was No. 12 on French magazine Slate's list of the "100 Most Influential Women of France", No. 68 on Total Film's list of "Top 200 Performances of All Time" for her performance in La Vie en Rose, and named "Best Dressed Star of 2013" by the British Grazia magazine.
Cotillard was mentioned in Trivia, an episode of The Office that aired in January, 2012. Her film, Les Jolies Choses, was the final answer to a trivia contest. Unlikely contestant Kevin Malone (portrayed by Brian Baumgartner) answers correctly and wins the contest. He credits Cotillard's multiple nude scenes in the film for his quick recall.