The Xbox One had a global install base of 39.1 million units as of March 31, 2018, according to market research outfit IHS Markit.
That figure (highlighted by Wall Street Journal reporter Sarah Needleman) encompasses all versions of the system, including the supercharged Xbox One X and the slimmer Xbox One S.
Microsoft has gained a reputation for being shy when it comes to sharing concrete sales figures, making IHS' figures all the more notable.
If accurate, they mean the Xbox One is someway behind the PlayStation 4, with IHS claiming Sony's flagship system had an install base of 76.6 million as of March this year.
Despite that apparent gulf, IHS analysts believe Microsoft's renewed focus on first-party content at this year's E3, where the company spotlighted a slew of exclusive titles and added five new studios to its in-house stable, will pay off in the long-term.
"It will take time to reap the rewards of this more expansion strategy," commented IHS' head of games research, Piers Harding-Rolls, "but it puts Microsoft on a much stronger footing."