Eugène Allonsius (born 12 December 1937) is a retired Belgian middle- and long-distance runner.

[1] During his career Allonsius set five national records.

[4] In addition to this, he competed as a guest athlete in the mile run at the 1966 South African championships and won that race.

[5] He won the long race at the 1963 World Military Cross Country Championships.

[7] In 1966 he established Allonsius Sport, a company specializing in athletics training and supplies.