Katherine’s international rowing career took off in 1997 when she raced in a coxless pair with Francesca Zino from Cambridge University and won the gold medal at the World under 23 Rowing Championships, setting a new record for the event. They were coached by Hamish Burrell who had coached Katherine at Edinburgh University. On their return home, Katherine and Francesca raced for seats in Britain’s senior women’s eight and went on to compete in that year’s World Championships where the Eight won bronze, the first time a British women’s Eight had medalled at World Championship level.

In 1999 Katherine raced in the quadruple sculls crew, finishing 7th at that year’s World Championships to qualify to boat the boat for the Olympic Games and the following year, at her first Olympic Games in Sydney, won silver in the quad, alongside fellow-Scot Gillian Lindsay and sisters Miriam and Guin Batten.

They were coached by Mike Spracklen.

In 2001 Katherine forged a new partnership with Cath Bishop to race in coxless pairs, now coached by Paul Thompson. This resulted in her first World title in 2003 when Katherine and Cath won gold at the World Championships in Milan, storming through the field from fourth to first in the last 600 metres, toppling the reigning World and Olympic champions from Romania.

The victory was a great breakthrough and hopes were high that they could add Olympic gold in Athens. However, throughout the 2004 season they could not defeat the experienced Romanians. In the Olympic final in Athens, the British pair could not catch the Romanians despite their traditional mid-course surge, which took them from fourth to second place and a superb silver medal.

Following Cath Bishop’s retirement, Katherine moved back to the quadruple scull in 2005.  That was a successful season with golds in the World Cups at Eton and Munich and culminating in a hard fought victory at the World Championships in Japan for the quad.

The World Cup Series in 2006 brought more success for the quad, with gold in all three stages, in Poznan, Munich and Lucerne.  The 2006 World Championships took place on home waters at Eton, which will be the Olympic rowing venue for the 2012 London Olympic Games.  In this final, Katherine’s crew fought an intense battle with Russia and were just beaten to the line in the dying metres of the race, to take silver. However, their Russian conquerors later fell foul of a drugs test and the British women’s quartet were restored, in January 2007, as rightful world champions once more.

In 2007, still at stroke in the quad, Katherine medalled at each of the World Cups and won the overall series title again. The quad then went on to successfully defend their world title at the World Championships in Munich. The quad was named ‘Female Crew of the Year’ by the International Rowing Federation.

Having raced in two World Cups in 2008, the focus for Katherine and her quad moved to the Beijing Olympics, where she won her historic third Olympic medal – silver.
Following the Beijing Olympic Games, Katherine took an extensive period away from the sport, but eventually decided to once again carry on the demanding lifestyle of a full-time rower, this time focused on the 2012 Olympic Games in London.

For the 2009 season, Katherine moved on to a new challenge and raced in the single sculls category for the first time internationally.

She won the opening World Cup event in Banyoles, Spain, but failed to medal in the next two World Cup rounds.  However, she stormed back with an outstanding performance at the World Championships in Poznan, Poland.  She led the field for most of the way but eventually, in increasingly choppy waters, she had no answer for the charge of reigning champion Ekaterina Karsten from Belarus, to cross the line in a deserved second place and added a precious silver world championship medal in the singles to her collection as well as shattering the existing British record for women’s singles sculls.

For the 2010 World Cup series Katherine raced in the double sculls with Anna Watkins and they then doubled up into the quad with Beth Rodford and Annabel Vernon for all three events. In Bled Katherine took gold in both races, in Munich she won gold in the double and silver in the quad and in Lucerne again won gold in both boats. This was an amazing achievement bearing in mind she and Anna had not much than an hour to recover between races.

At the 2010 World Championships on Lake Karapiro, Katherine and Anna raced superbly, winning gold over six seconds ahead of second place.

Katherine and Anna were subsequently named 2010 World Rowing Female Crew of the Year. The duo, coached by Paul Thompson were described by the sport’s governing body as ‘the perfect combination’. She was named the ‘Olympic Athlete of the Year for 2010 for the sport of rowing receiving the British Olympic Association trophy at the GB Rowing Dinner.

In Munich at the first World Cup of 2011 Katherine with Melanie Wilson substituting for injured for injured Anna Watkins won gold in the women’s sculls with clear water between them and the boats of USA and Belarus. In Lucerne, Katherine was reunited with Anna to win gold again and to win the overall World Cup Series in the double.

At the 2011 World Rowing Championships in Bled, Katherine with Anna maintained their title as World Champions by leading their race from the start.

At the 2012 GB Rowing Team Senior Trials, Katherine won the women’s single scull, making her success in National trials now a record tally of ten. Katherine and Anna then won all three World Cups that year: in Lucerne, Belgrade and Munich.

Success came at the London 2012 Olympic Games at Dorney Lake where Katherine and Anna took the Gold medal in the double sculls. They crossed the line with clear water between them and nearest rivals Australia with Poland in bronze and were buoyed by a thunderous home crowd for more than half the 2000m course.

After a 2 year break, Katherine returned to international rowing and at the 2015 World Rowing Championships, she and partner Vicky Thornley successfully qualified the double scull boat for the Olympic Games in Rio in 2016. A period of turmoil and unrest followed which saw Katherine and Vicky have their boat disbanded, an unsuccessful trial for the women’s 8 boat and at the eleventh hour, the reformation of the double scull. As Rio loomed, Katherine and Vicky were not named in the initial selection for the Team GB rowing squad but successfully proved themselves a fortnight later.

There was little expectation that the double would find form in time for the Olympic Games but the girls put an early marker down coming second in both their heat and their semi-final.

On the 11 August 2016 Katherine Grainger and Vicky Thornley set off down the 2000m course in the Olympic final, leading the field for the first 1500m. They were overtaken by Poland in the final moments of the race, crossing the finish line 1.05 seconds off the Polish crew.

Considering that many did not expect this pairing to even make it to Rio, when they crossed the finish they not only won a silver of Goliathan proportions but the result propelled Grainger into the all-time records books.