Rooney Mara steps out for a solo hike months after welcoming son River with fiance Joaquin Phoenix

New mom Rooney Mara steps out for a solo hike in Los Angeles months after welcoming son River with fiance Joaquin Phoenix

She became a mom in 2020.

And, Rooney Mara was enjoying some time alone on Friday while getting fresh air during a hike in the Studio City area of Los Angeles.

The 35-year-old actress and her fiance, star Joaquin Phoenix, welcomed their son, River, sometime around September of last year.

Mom’s day out: Rooney Mara was enjoying some time alone on Friday while getting fresh air during a hike in the Studio City area of Los Angeles

Rooney looked ready for her workout in a pair of black spandex leggings, black hiking shoes, a baggy white T-shirt and a blue and green flannel.

To protect herself from the coronavirus, the Girl with the Dragon Tattoo star donned a white N95 mask and some sunglasses.

Her dark hair was pulled back into a loose, low bun and the new mom was solo for her hike.

Rooney is just a few months postpartum as she and Joaquin welcomed their first child together last fall, naming him after Joaquin’s late brother River Phoenix, who died at 23 years old in 1993.

Fitness: Rooney looked ready for her workout in a pair of black spandex leggings, black hiking shoes, a baggy white T-shirt and a blue and green flannel

Fitness: Rooney looked ready for her workout in a pair of black spandex leggings, black hiking shoes, a baggy white T-shirt and a blue and green flannel

Family life: Rooney is just a few months postpartum as she and Joaquin welcomed their first child together last fall, naming him after Joaquin's late brother River Phoenix, who died at 23 years old in 1993

Family life: Rooney is just a few months postpartum as she and Joaquin welcomed their first child together last fall, naming him after Joaquin’s late brother River Phoenix, who died at 23 years old in 1993

Director Victor Kossakovsky spilled the beans at the 2020 Zurich Film Festival in September, after a screening of the film Gunda, on which Joaquin served as executive producer.

He slipped in the news during a Q&A, after he was asked how he got the new dad involved in the film: ‘He just got a baby by the way… A beautiful son called River.’

River died at the peak of his career, with memorable roles in Stand By Me (1986), Indiana Jones and the Last Crusade (1989), and Gus Van Sant’s My Own Private Idaho (1991) already under his belt. 

Low key: Joaquin and Rooney subtly confirmed the news of their firstborn's arrival in November, when they mentioned him in an op-ed for People about the migrant children crisis

Low key: Joaquin and Rooney subtly confirmed the news of their firstborn’s arrival in November, when they mentioned him in an op-ed for People about the migrant children crisis

They subtly confirmed the news of their firstborn’s arrival in November, when they mentioned him in an op-ed for People about the migrant children crisis.

Rooney began dating her Her (2013) costar in late 2016, and they later starred together in Don’t Worry, He Won’t Get Far on Foot and Mary Magdalene, both of which premiered in 2018.

The animal rights advocates live in the Hollywood Hills with their two dogs Soda and Oskar, and their engagement was confirmed in July of 2019, a few months after she was first spotted wearing her engagement ring.

Mom and dad: Rooney began dating her Her (2013) costar in late 2016, and they later starred together in Don't Worry, He Won't Get Far on Foot and Mary Magdalene, both of which premiered in 2018 (Pictured in 2019)

Mom and dad: Rooney began dating her Her (2013) costar in late 2016, and they later starred together in Don’t Worry, He Won’t Get Far on Foot and Mary Magdalene, both of which premiered in 2018 (Pictured in 2019)