Sin Kim-dan or Shin Keum-dan (Korean: 신금단; romanised Sin Kim Dan in English in the 1960s) (born 30 July 1938^[1]) is a North Korean former track and field athlete who competed in the 1960s in the women's 200 m, 400 m and 800 m, setting disputed world records in the latter two events.

Sin worked as a lathe operator.^[2] She was separated from her father in 1950 during the Korean War. He lived in South Korea.^[3] She was described as tall and long-striding.^[2]

Excluding 1965, Sin was ranked in the top 10 in the world from 1959 to 1967 at 400 m,^[4] and from 1960 to 1967 in 800m.^[5] In October 1960, she surpassed the 400 metres world record with an unratified time of 53.0.^[6] She won the 400 m at the Brothers Znamensky Memorial meeting in Lenin Stadium, Moscow, in 1961, 62, and 63.^[7] At Pyongyang in 1962, she ran 400 m in 51.9 s, becoming the first woman to break the 53-second barrier and 52-second barrier.^[8] Of her eight claimed world record marks, this would be the only one ratified.^[9][10] A note in the 1964 British Athletics yearbook states, "The IAAF are withholding recognition of a time of 53.1 by Betty Cuthbert on 11.3.63 pending investigation of Sin Kim Dan's 51.9; meanwhile there is no official world record."^[11]

Sin represented North Korea at the GANEFO (Games of the New Emerging Forces) in 1963 and 1966, winning gold in the 200 m, 400 m, and 800 m at both games.^[12] Her 1963 times of 51.4 (400 m) and 1:59.1 (800 m) bettered the world records, the latter the first woman under 2 minutes.^[13] They were never ratified by the IAAF, however, as GANEFO was not an approved competition.^[14]

Sin's personal bests were set in 1964 in Pyongyang, at 51.2 for 400 m and 1:58.0 for 800 m.^[1][14] The IAAF suspended GANEFO competitors, effectively barring Sin from the 1964 Summer Olympics in Tokyo.^[3][15] Sin was reunited with her father at Haneda Airport for a few minutes before being turned back from Japan.^[3] Ann Packer won the Olympic 800 m in a new official world record of 2.01.1.^[16]

In 1966, Time magazine stated in an article on the introduction of gender verification in sports:^[17]

Finally there was Sin Kim Dan, a delicate little North Korean lass who broke the women's records at both 400 meters and 800 meters two years ago; some time later, an overjoyed elderly gentleman in South Korea recognized Sin as the son he had lost in the war.

This claim has been repeated since.^[18][19]

Sin was one of the first awarded the title "People's Athlete" after its creation in 1966 by the Supreme People's Assembly.^[20]

• Women's 400 metres world record progression
• 800 metres world record progression#Women

• Derun, P. "Training Experiment of Sin Kim Dan". Track Technique—The Journal of Technical Track & Field Athletics (48).