After swimming at the European Junior Championships in 2005, Kromowidjojo won a gold medal as a member of the 400m freestyle relay at the 2006 European Championships.
2008 Olympics / European Championships / FINA Short Course World Championships
Qualifying for her first Olympics at just 17 years old, Kromowidjojo won a gold medal as a member of the 400m freestyle relay.
In the same year, the relay won gold at the 2008 European Championships and set a new world record in the 800m freestyle relay at the FINA Short Course World Championships.
2009 World Championships
In 2009 she picked up another world record at the FINA World Championships as a member of the 400m freestyle relay.
2010 World Short Course Championships
Kromowidjojo won gold in her individual events, the 50m freestyle and 100m freestyle, setting a championship record in the 100.
2012 London Olympics
At the 2012 London Olympics, Kromowidjojo had a phenomenal meet, winning both the 50m Freestyle and the 100m Freestyle. She set Olympic Records in the 50m Freestyle final, the 100m semifinals, and the 100m final. She was the first Dutchwoman since 2000 to win an Olympic Gold in the 50m freestyle.
In light of her record setting performances, The European Swimming Federation named her the 2012 Female European Swimmer of the Year.
Leading up to the 2016 Rio Olympics, Kromowidjojo consistently sprinted to top 10 times in the 50m Freestyle globally.
2016 Rio Olympics
Kromowidjojo finished sixth in the finals of the 50m Free just .08 out of medaling. In the 100m Free, Kromowidjojo touched 5th, this time .09 seconds behind bronze medalist, Sarah Sjostrom of Sweden.
2016 FINA World SCM Championships
Kromowidjojo outsprinted the field in the 50m free with a time of 23.60, beating Silvia Di Pietro (Italy) by .30 and Madison Kennedy (USA) by .33. In the 100m Free, Kromowidjojo finished .11 seconds behind Gold Medalist, Brittany Elmslie of Australia. She also picked up another silver medal in the Women’s 4x50m Free Relay, bronze in the Women’s 4x100m Free Relay, and silver in the Mixed 4x50m Free Relay.
On day 5 of the meet, Kromowidjojo finished fifth with a time of 52.78, just 0.01 seconds behind fourth place finisher, Mallory Comerford of the US, and just off her best time of 52.75.
On day 7, Kromowidjojo pulled up for silver in 25.38 in the women’s 50 fly behind Sarah Sjostrom,who accelerated to gold by nearly eight tenths of a second in 24.60.
On day 8, in the final of the 50m freestyle, Kromowidjojo broke through 24.0 for the first time, going 23.85 to take the silver, again behind Sjostrom. With that best time, it was also a new Dutch record.
In the women’s 4x100m freestyle relay, Kromowidjojo swam the anchor on the Netherlands bronze medal winning relay. Teaming with Kim Busch, Femke Heemskerk and Maud Van Der Meer, Kromowidjojo split an impressive 51.98 to over take Sweden and hold off Canada. Ranomi’s split was the fastest of the field aside from Sarah Sjostrom’s lead off leg of 51.71, which was a world record.
Also swimming the anchor on the 4×100 Mixed freestyle relay, Kromowidjojo teamed with Ben Schwietert, Kyle Stolk and Femke Heemskerk to win the Silver Medal behind the US.
2017 SCM European Championships
Kromowidjojo competed in her usual range of events in Copenhagen, Denmark. She touched the wall first in 50 butterfly and 100 freestyle and finished second in 50 freestyle only 0.01 seconds behind Sarah Sjöström. Her win in the 50 butterfly came in a dramatic fashion after Sjöström missed the final. In the 100 freestyle, she broke the Championship Record with a time of 50.95.
She was also apart of three record breaking relays. Netherlands broke the World Record in the mixed and women’s 4×50 freestyle relays. The third win did not come easily as all top three teams were within 0.04 seconds in the mixed 4×50 medley relay. Kromowidjojo managed to touch the wall first and team Netherlands finished with a time of 1:37.71 which was a new Championship Record.
2018 European Championships
In Glasgow, Ranomi earned even more international medals even though she was not at top form. Her 3rd place finish and bronze medal in the 50 free was complimented by a pair of silvers in the 400 and mixed 400 free relays.
2018 World Short Course Championships
Ranomi was back on top in Hangzhou, winning 3 individual golds in the 50 free (23.19), 100 free (51.14), and 50 fly (24.47), breaking championship records in all 3 and a national record in 50 fly. She added 5 relay medals to her haul, including silvers in the 4×50 free, 4×100 free, mixed 4×50 free, and mixed 4×50 medley, and a bronze in the 4×50 medley relay.
2019 World Championships
Kromowidjojo won her first medal of the championships on Day 7, touching for silver in the 50 fly (25.35) after missing the final of the 100 free.
2021 European Championships (Budapest, Hungary)
Ranomi took wins in the 50 free (23.97) and 50 fly (25.30), along with silvers in the 400 free relay, mixed 400 free relay, and mixed 400 medley relay. She also finished 4th in the 100 free (53.44) by .01.