Niklas Arrhenius (born September 10, 1982) is an American-Swedish track and field athlete who competes in the discus throw and shot put. He represented Sweden in the discus at 2008 Summer Olympics, was a four-time competitor at the World Athletics Championships (2007, 2011, 2013, 2017), and competed at five consecutive editions of the European Athletics Championships from 2006 to 2016. At the Swedish Athletics Championships he won seven national titles in discus, and was an eight-time champion in the shot put (combined indoors and outdoors).