Maria "Rie" Vierdag (22 September 1905 – 17 July 2005) was a Dutch freestyle swimmer who competed at the 1924, 1928 and 1932 Summer Olympics.

She won a silver medal in the 4×100 m relay in 1932, setting a European record, and finished sixth in 1924.

In 1927 she finished her 100 m race in the same time as Joyce Cooper, and an addition trial was arranged between them.

Cooper was too tired to attend it, and Vierdag was announced as the winner.

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