Per-Olof "Posa" Serenius (born 9 March 1948 in Hedemora, Sweden) is a Swedish ice speedway rider who has won gold in the World Championships a number of times.
In 2009, he won his 20th gold medal in the Swedish Championships.
His list of accomplishments includes two individual golds in the World Championships in 1995 (Inzell) and 2002 (Lillehammer) and three team golds in 1985, 1995, 2002.
He participated in the documentary film Icy Riders from 2008.