Mikko Ilonen (born 18 December 1979) is a retired Finnish professional golfer who played on the European Tour, winning five times. He is considered to be the most successful golfer from Finland.

Ilonen was born in Lahti, Finland. He won the 2000 Amateur Championship, and turned pro in 2001. He played mainly on the European Tour, where he won five events.

He won his first professional tournament at the 2007 Indonesia Open, an event co-sanctioned by the European Tour and Asian Tour. He was the first Finn to win a European Tour event and to feature in the top 100 of the Official World Golf Ranking.

In June 2013, Ilonen won the Nordea Masters event in Sweden for the second time in his career and third tour level victory overall.

In June 2014, Ilonen won the Irish Open at Fota Island in Cork. Ilonen led the tournament from start to finish and ended up one shot clear of Italian Edoardo Molinari.

Ilonen's best major championship finish was tied 7th at the 2014 PGA Championship. In 2014 he finished the season in a career best 18th on the European Tour Order of Merit.

In March 2019, Ilonen announced his retirement from tour golf.

¹Co-sanctioned by the Asian Tour