The Eagles [ tickets ]' "Their Greatest Hits 1971-1975" has been certified by the Recording Industry Association of America for sales in excess of 27 million copies, making it the top-selling album in U.S. history.

The certification came just days after the RIAA announced that Michael Jackson’s "Thriller" had surpassed the 26 million sales mark and had pulled into a tie with the Eagles’ set, which was first released in 1976.

"The unprecedented feat of selling 27 million records speaks volumes about [the Eagles’] legions of fans and the fact that this is simply one of those 'must have' albums," RIAA President and CEO Hilary Rosen said in a statement.

"Thriller" held the RIAA record as the top-selling album from 1984 until 1999, when the Eagles tied, then surpassed, its sales mark. Then, last month, "Thriller" climbed back into a tie with the Eagles.

Third on the RIAA's list of top-selling albums is Pink Floyd’s "The Wall" (23 million). It is followed by Led Zeppelin "IV" (22 million), Billy Joel’s "Greatest Hits Volume I & Volume II" (21 million), and Fleetwood Mac's "Rumors" (18 million).

The RIAA awards its gold (500,000 units shipped) and platinum (1,000,000 units shipped) certifications after an independent audit is conducted by the accounting firm Gelfand, Rennert & Feldman. Record companies typically must pay a fee to the RIAA before the audit is conducted, so an album’s certification level doesn’t necessarily track sales levels exactly.

Unlike other sales-tracking services like SoundScan, which tracks retail sales, the RIAA’s certification process counts all units shipped--including those distributed through record clubs--minus returns and promotional copies.

Earlier this week, the Eagles announced plans to release a 4-CD box set. One of the set's discs will feature a dozen live tracks that were recorded last year, all of which the band plans to release as free downloads to help promote the compilation.