Judges for the prize, who have previously only ever singled out buildings, went against the grain to include the wider public realm, said multidisciplinary practice BDP.
"By nominating the 17ha masterplan they broke with tradition and put the scheme on a par with iconic structures for the first time in the prize's 13-year history," said a representative for the practice.
Stirling judges said Liverpool One "single-handedly reversed the fortunes of the city by bringing a new social and economic vibrancy to derelict but historic buildings".
The result was a "vibrant and economically successful mixed-use quarter - an entirely revitalised city centre". BDP laid "generous public-space networks", judges said.
A 2ha park helps link nearly 40 new buildings including shops, a large cinema, restaurants, cafes and bars, 600 flats, two hotels and offices.
Head of BDP's northern retail team Terry Davenport said: "Being responsible for the first-ever masterplan to make the shortlist is a fantastic achievement."
He added: "It also helps build better and more coherent communities and, if done well, can genuinely make a difference to the quality of people's lives."
Judges praised developer Grosvenor for delivering "sufficient critical mass to regenerate a city and commitment to design excellence and urban coherence".
BDP worked with several designers including Pelli Clarke Pelli, Allies & Morrison and Austin-Smith:Lord. The Stirling Prize event will be held in London on 17 October.