Kinsella, 40, is leaving to "fulfill a long-held dream to help build an Internet-based international brand," according to a Microsoft spokeswoman. He will join Netherlands-based World Online as chairman elect June 1 and will officially leave Microsoft on May 19, the company said.
"We're sorry to see him go and wish him the very best," spokeswoman Kim Kuresman said.
The departure comes as the online news service lays the groundwork for an initial public offering. The company confirmed in March that it has met with investment banks to discuss plans for taking its Internet business public, which could give it leverage in the competitive online publishing market.
John Nicol, MSNBC.com general manager, and editor in chief Merrill Brown will continue to run the site's day-to-day operations until a replacement is made, Kuresman said. In addition, Jed Savage will assume Kinsella's role as national sales manager for MSN.
At World Online, Kinsella is charged with restoring confidence in one of Europe's largest Internet service providers, with more than 2.2 million subscribers.
A scandal related to World Online founder Nina Brink's sale of most of her 6.35 percent stake in the company months before the public offering led to her resignation and played havoc with the company's stock. Shares fell from their listing price of 43 euros ($38.75 U.S.) March 17 to a low of 11.20 euros ($10.10 U.S.) May 5. First-quarter losses doubled at the company.
In early 1999, Microsoft's consumer group, headed by Rick Belluzo, created the chief executive and president positions for Kinsella at MSNBC's online division, a joint venture of Microsoft and NBC. Kinsella joined Microsoft in 1996 after working as the editor of Time Warner's Pathfinder.
Reuters contributed to this report.