Hima Das was born at Kandhulimari village, near the town of Dhing in the state of Assam to Ronjit Das and Jonali Das. They belong to the indigenous Kaibbarta community of Assam. Her parents are farmers by profession. She is the youngest of five children. She attended the Dhing Public high School and was initially interested in playing football. She used to play football with the boys at her school and had always wanted to pursue a career in football. However, she did not see any prospects for herself in women's football in India. Later, upon advice from a school physical education teacher, she changed to sprint running.
In April 2018, Das competed in the 2018 Commonwealth Games at Gold Coast, Australia, in the 400 metres and the 4×400 metres relay. On 12 July 2018, Das won the 400 m final at the World U-20 Championships 2018 held at Tampere, Finland, clocking 51.46 seconds and becoming the first Indian sprinter to win a gold medal at an international track event. At the 2018 Asian Games, Das qualified for the 400 m final, after clocking 51.00 in heat 1 and setting a new Indian national record. On 26 August 2018 she improved the national record to 50.79 s in the 400 m final however she could win only the silver medal. Later on 30 August 2018, she, along with M. R. Poovamma, Sarita Gayakwad and V. K. Vismaya won the women's 4 × 400 metres relay clocking 3:28.72. Hima also won a silver medal in the 4 × 400 m mixed relay, which was held for the first time at Asian Games. The medal was later upgraded to gold after Bahrain team was suspended due to doping violations. Das continued her success in 2019 winning the 200m gold in Poznan Athletics Grand Prix in Poland, on 2 July 2019, with a time of 23.65 seconds. On 13 July, she won 200m gold at the Kladno Athletics Meet in the Czech Republic with a time of 23.43 seconds. On 20 July 2019, she achieved her third gold in a month, and fifth gold, in her 400-meter race in Nové Město, Czech Republic completing the race in 52.09 seconds. She was named for the World athletics championships to be held at Doha in October 2019. However a month before, she was ruled out of participation due to a back problem that started after she competed at the Asian games the previous year.
