The prototype spacesuits and accompanying boots were revealed at the Foster + Partners-designed Spaceport America in New Mexico today.
Y-3's all-in-one navy flight suit is made from a heat-resistant synthetic material called Nomex Meta Aramid, which is woven using a 3D-engineered pattern.
The suit zips up at the front of the torso, and also opens up the shins. It has been tailored to support a pilot's natural seating position, identified through a series of tests with Virgin Galatic's team.
"The pilot flight-suit prototype that we have developed truly represents both of our brands and, more importantly, will ensure comfort, functionality and support for the pilots of the world's first commercial space flights," said Y-3 senior design director Lawrence Midwood.
Y-3 has also developed lace-up boots made from leather and Nomex, with outsoles designed for grip and heel inserts for added comfort and shock absorption.
Pilots will begin trialling the apparel during Virgin Galactic's flight test programme, and their feedback will be used to optimise the designs.
Virgin Galactic's SpaceShipTwo craft completed its first rocket-powered flight in 2013, but the company set up by British entrepreneur Richard Branson suffered a setback when one of its vehicles crashed a year later.
The company plans to take commercial passengers to space by the end of 2017.
Virgin Galactic's collaboration with Y-3 also includes a limited-edition jacket for the pilots, and will eventually extend to garments for crew and passengers.
"Our evolution into a fully functioning spaceline presents unprecedented opportunities to create original designs in support of our unique customer experience," said Virgin Galactic head of design Adam Wells.
"We will explore the potential to create innovative apparel and accessories – both for our staff and for our pioneering customers – that is appropriately functional and fit-for-purpose, is thoughtfully and elegantly crafted, and is fulfilling and fun to wear and use."
Y-3 was set up by Japanese fashion designer Yamamoto and German sports brand Adidas in 2001. Its designers have previously collaborated with graphic designer Peter Saville to prints for its Spring Summer 2014 collection and a line of trainers.