Donna Marie Theresa Air was born on 2 August 1979, in Wallsend, North Tyneside, to receptionist Marie (née Lackenby) and mechanical engineer Trevor Air. The eldest of three children, Air has a sister, Francesca, and brother, Alexander. Air grew up in Gosforth, Newcastle upon Tyne, where she attended St Oswald’s Catholic Primary School and later Sacred Heart Convent School. Air was then educated at Gosforth High School, and also attended First Act Theatre, a local youth theatre group. Her fellow students at First Act Theatre included Jill Halfpenny and Anthony McPartlin. Air also modeled as a child, appearing in ads for Nissan, Asda and Lenor.

First appearing as an extra on CBBC programme Byker Grove aged 10, Air was asked to audition for a role by a producer, and was subsequently cast as Charlie Charlton. In 1994, Air and her co-stars Jayni Hoy and Vicky Taylor formed Byker Groove!, releasing the single “Love Your Sexy”, which charted at 48 on the UK Singles Chart. Air moved to London aged 15, subsequently becoming part of pop duo Crush with Jayni Hoy. Two of the band’s singles released in 1996, “Jellyhead” and “Luv’d Up”, charted in the UK at 50 and 45 respectively, while their debut studio album Teenage Kicks failed to chart. The band’s management team booked Crush on a tour of the United States, Japan and South East Asia, commencing after Air completed her GCSEs, with “Jellyhead” subsequently peaking at 76 on the Billboard Hot 100.

Following her promotional touring, she returned to the United Kingdom and in September 1997 signed to MTV UK to host the daily live show, MTV Select, later becoming a presenter of several shows including The Big Breakfast, Channel 4’s flagship morning entertainment show. Air departed MTV Select in April 2000, citing her desire to return to acting and to devote more time to her role on The Big Breakfast as the reasons for her departure. In January 2001, Air was promoted to a main presenter on The Big Breakfast in a relaunch of the programme amid falling viewer figures. However, Air later resigned in May of that year, with Channel 4 axing The Big Breakfast shortly thereafter. Also in May, Air appeared in The Mummy Returns, the sequel to The Mummy (1999), in a “blink-and-you’ll-miss-it cameo” that BBC film critic Neil Smith described as one of the only points of difference between the sequel and the original film.

In 2000, Air met businessman and animal conservationist Damian Aspinall, having been introduced by their mutual friend Tara Palmer-Tomkinson. The pair began a long-term relationship, with Air giving birth to their daughter, Freya Air Aspinall, in September 2003. Shortly after her birth the couple announced their intention to place their baby daughter in the care of a gorilla, a ritual in which Aspinall’s older children had already taken part. Air and Aspinall separated amicably in 2007. In 2013, Air began dating James Middleton, the younger brother of Catherine, Duchess of Cambridge; the pair eventually separated in 2018. Air lives in Chelsea, London.

In January 2013, Air participated in the ITV programme Splash! She replaced Jennifer Metcalfe at short notice. In November 2017, Air announced that she would be taking part in the tenth series of Dancing on Ice. She was partnered with Mark Hanretty. They were eliminated in Week 7.

In 2019, Air was announced as having a starring role in the second series of the drama The Split, which started airing on BBC One in February 2020.