Christina ("Stien") Wilhelmina Baas-Kaiser (born 20 May 1938) is a former speed skater from the Netherlands.
She was not selected for the 1964 Winter Olympics because of her 'old age' (25 at that time), but later turned out to be the first Dutch female world class speed skater. In both 1965 and 1966, she won bronze at the World Allround Championships. After having become World Allround Champion twice (in 1967 and 1968) – and also winning her 3rd and 4th Dutch Allround Championships those years – she participated at the 1968 Winter Olympics in Grenoble. Her two bronze medals – on the 1,500 m, behind Finnish skater Kaija Mustonen and Dutch compatriot Carry Geijssen, and on the 3,000 m behind compatriot Ans Schut and, once more, Kaija Mustonen – were a bit disappointing. Not she, but Geijssen (who not only won silver on the 1,500 m, but also gold on the 1,000 m) and Schut became the Dutch heroines of those Olympics.
Although she was still a formidable competitor in the years that followed, Kaiser was slightly surpassed at major championships by Atje Keulen-Deelstra, who was the same age as Kaiser. In 1972, by then married and 33 years old, Baas-Kaiser was no longer really considered to be a favourite, especially not after her disappointing 11th place at the European Allround Championships. At the 1972 Winter Olympics in Sapporo, Baas-Kaiser originally was not meant to skate, but since fellow Dutch skater Trijnie Rep had disappointed on the 500 m (finishing 20th) and the 1,000 m (finishing 24th), Baas-Kaiser was given a chance on the 1,500 m and the 3,000 m. And she turned it into something beautiful: On the 1,500 m, she won silver behind Dianne Holum, but ahead of Atje Keulen-Deelstra, and on the 3,000 m two days later, she became Olympic Champion ahead of Holum and Keulen-Deelstra. She ended her skating career later that year with a silver medal at the World Allround Championships.
Nationally, she won the allround titles in 1964, 1965, 1967–1969 and 1971, finished second in 1970 and 1972, and third in 1966. In 1967, she was chosen the Dutch Sportswoman of the Year. She is a niece of the Olympic speed skater Kees Broekman.
Over the course of her career, Baas-Kaiser skated nine world records and twenty-seven Dutch records: