The event was first reported by CNBC, but Yahoo later confirmed that it has invited members of the media to an early evening press conference.
The Monday gathering is scheduled for 5 p.m. ET, and the invite reads, "Join us as we share something special." A Yahoo spokesperson said the company would also livestream the announcement, but declined to share additional information on the subject of the event.
Yahoo could use the hastily scheduled affair to announce some type of deal with Tumblr, a New York-based startup that plays host to about 108 million blogs. The companies are said to be actively discussing a partnership with a $1 billion buyout on the table.
Update, 4:46 p.m. PT: If you're expecting big Tumblr news, you might be underwhelmed as Bloomberg reports the event will feature a product update for Flickr.