In 2019, Billboard‘s staff revealed its picks for the greatest pop star of every year dating back to 1981 (the first year of MTV, essentially the birth of the modern pop era), with essays making the case for each as the biggest, brightest and most important star in their solar system that calendar year. For the last few years, we’ve also counted down our picks for the 10 greatest pop stars of the 12-month period, with each getting their own year-in-review tribute from one of our staffers. (Our picks for the No. 1 Greatest Pop Star of the Year this decade have included BTS, Bad Bunny and Taylor Swift.)

But with the quarter-century mark coming up, we decided it was a good time to zoom out a little bit on the whole last 25 years in pop stardom. And so this week, we begin our countdown of the 25 Greatest Pop Stars of the 21st Century: a list attempting to take stock of the pop stars who have been most important and most impactful in the U.S. over that timespan. We will be unveiling our list over the course of the next four months, unveiling one or two artists a week, along with our usual essays commemorating each artist — as well as additional articles focusing on different aspects of their careers and rounding up their chart achievements, and regular podcast and video discussions of our chosen stars’ careers and legacies. We hope it will all serve to properly celebrate the 25 artists who have most defined the pop music and pop culture of the first 25% of this century, and to help provide an accurate snapshot of how the sound, look and overall meaning of pop superstardom have evolved over that period.

First, however — we must acknowledge that 25 is simply nowhere near a big-enough number to properly acknowledge all the pop stars who have dominated the charts and moved the culture since Y2K. So with that in mind, we’re starting off our rollout of this project with a quick unranked list of our Honorable Mention picks for the best of the rest: the 25 pop stars who were great enough to get strong consideration for our top 25, but ultimately just didn’t quite have either the stats, the impact, the longevity or the volume to elbow their way into our main list. We love ’em all just the same, and we couldn’t kick off this project in earnest without giving them their proper due first.

And we must also issue our obligatory reminder that unlike with our Year-End Charts, these Greatest Pop Stars are NOT mathematically determined by stats like chart position, streams or sales numbers. Those play a big part in our final rankings, of course — you can’t be one of the greatest pop stars of the century without great pop hits and great pop albums — but so do things like music videos, live performances and social media presence, and more intangible factors like cultural importance, industry influence and overall omnipresence. (And we’re measuring this over all 25 years of this century so far, so if you were only heard from at the beginning or the end of that period — or only had one or two big songs, albums or eras — that’s gonna significantly hinder your ranking here as well.)

Here are our 25 picks, presented alphabetically, for the closest-but-not-quite pop stars — the Nos. 26-50 Greatest Pop Stars of the 21st Century, essentially — and check back throughout the next few months as we count down our top 25, and officially name our Greatest Pop Star of the 21st Century this autumn.