The couple said they were “floating with love and wonder” after their daughter’s “safe and healthy arrival”.
The pair also shared a black-and-white picture of them holding Daisy’s tiny hand.
Perry revealed she was pregnant in the music video for her single Never Worn White earlier this year.
Welcome to the world, Daisy Dove Bloom! We are honoured to introduce Goodwill Ambassadors @KatyPerry and Orlando Bloom's new bundle of joy.
“We are floating with love and wonder from the safe and healthy arrival of our daughter."
— UNICEF (@UNICEF) August 27, 2020
“We are floating with love and wonder from the safe and healthy arrival of our daughter,” the couple said in a statement released via Unicef, a charity supporting disadvantaged children, for which both Perry and Bloom are ambassadors.
“But we know we’re the lucky ones and not everyone can have a birthing experience as peaceful as ours was.
“Communities around the world are still experiencing a shortage of healthcare workers and every 11 seconds a pregnant woman or newborn dies, mostly from preventable causes.
“Since Covid-19, many more newborn lives are at risk because of a greater lack of access to water, soap, vaccines and medicines that prevent diseases. As parents to a newborn, this breaks our hearts, as we empathise with struggling parents now more than ever.”
The couple said they had set up a donation page to mark Daisy’s birth, with the money going towards new mothers and their children.
“We hope your heart can bloom with generosity,” they added.
Earlier this month Perry, whose new album Smile is released on Friday, described being pregnant during a pandemic as an “emotional rollercoaster”.
The singer announced her pregnancy in the video for Never Worn White, revealing a baby bump in the final frames of the four-minute clip.
The song’s lyrics hinted that she and Bloom planned to walk down the aisle soon, after getting engaged on Valentine’s Day last year.
US singer Perry, who was previously married to Russell Brand, shot to fame in 2008 with the single I Kissed A Girl, which reached number one in the UK.
Her hits since then have included Roar, California Gurls, Firework and Never Really Over.
Bloom was previously married to Australian model Miranda Kerr, and they have a son, nine-year-old Flynn.
The British actor has starred in Pirates Of The Caribbean, The Lord of the Rings and The Hobbit.