Carl Marcus Joakim Hellner (born 25 November 1985) is a Swedish former cross-country skier who competed between 2003 and 2018.

Hellner won bronze, his first medal, in the 4 × 10 km relay at the 2007 FIS Nordic World Ski Championships in Sapporo.

A couple of days later, Hellner, like in the 2010 Winter Olympics, rode the last lap for Sweden in the 4 × 10 km relay.

In the 2012, Hellner became the first Swedish male skier to be on the podium in Tour de Ski by securing a second place overall after passing Petter Northug in the final uphill event.

In March 2012, Hellner joined Team Pokerstars SportsStars alongside Mats Sundin and Boris Becker.