Toby Webster, who runs The Modern Institute in Glasgow, a gallery which also represents a group of leading Scottish artists, has cemented his position in the Art Review Power 100.
Webster has been named the 51st most powerful person in the art world, above the Turner Prize-nominated artist Tino Sehgal, and American artist Jeff Koons.
Elsewhere in the list, the artist and film maker Steve McQueen is at number 36, up from 59: his work directing the movie 12 Years A Slave is currently being lauded in the US. Mr Webster has long been considered one of the key movers in the art scene, an influential gallerist and agent who staged his first show in his flat.
His company represents Martin Boyce, who won the Turner Prize in 2011, Richard Wright, winner in 2009, and Simon Starling, who picked up the prestigious contemporary art prize in 2005, as well as Jeremy Deller, who represented the UK at this year's Venice Biennale.
The sister of one of the world's richest men tops the list. Sheikha Al Mayassa bint Hamad bin Khalifa Al Thani is the sister of the Emir of Qatar and heads the country's museums authority. It sponsored the record-breaking Tate Modern Damien Hirst exhibition, which attracted 463,087 visitors during its run last year.
Sheikha Al Mayassa first appeared on the Power 100 in 2011 at number 90 and rose to number 11 last year.
David Zwirner, who owns galleries in London and New York, is in second place, with his former business partner Iwan Wirth placed third.
This year's list puts Tate director Nicholas Serota at number six, one place behind Hans Ulrich Obrist and Julia Peyton-Jones, who run London's Serpentine Gallery.