Ellen Walshe (born 29 September 2001) is an Irish swimmer. She competed at the 2020 Summer Olympics in the 100 metre butterfly and the 200 metre individual medley. At the 2021 World Swimming Championships, she won the silver medal in the 400 metre individual medley. She was the first swimmer representing Ireland to win a medal higher than a bronze medal at a World Swimming Championships. Collegiately, she competes for the Tennessee Volunteers.

Walshe started attending the University of Tennessee in 2021, where she competes as part of the Tennessee Volunteers swim team.

When Walshe was 13 years old, she won the silver medal in the 100 metre butterfly with a time of 1:02.17 at the 2015 European Youth Summer Olympic Festival held in Tbilisi, Georgia in July and August 2015.

In July 2019, at the 2019 World Aquatics Championships in Gwangju, South Korea, Walshe placed 35th in the prelims heats of the 100 metre butterfly on the first day of competition with a time of 1:00.85. Three days later, she placed 19th in the prelims heats of the 4×100 metre mixed medley relay swimming the butterfly leg of the relay in a 1:00.89 and achieving a time of 3:53.69 with her Ireland relay teammates Conor Ferguson (backstroke), Niamh Coyne (breaststroke), and Robert Powell (freestyle).

On 23 May 2021, at the 2020 European Aquatics Championships held at Danube Arena in Budapest, Hungary, Walshe set a new Irish record in the 4×100 metre medley relay with Danielle Hill, Mona McSharry, and Victoria Catterson at 4:02.93 and placed 11th overall. Three days earlier she split a 1:001.18 on the butterfly leg of the 4×100 metre mixed medley relay to help place 13th and achieve a new Irish record time of 3:49.08 with Shane Ryan, Darragh Greene, and Danielle Hill.

At the 2020 Summer Olympics in Tokyo, Japan, and delayed to 2021 due to the COVID-19 pandemic, Walshe won her heat, placed 24th overall, and did not advance to the semifinals in the 100 metre butterfly with her time of 59.35 seconds. In her second and final event, Walshe placed 19th overall in the 200 metre individual medley prelims heats with a time of 2:13.34 and finished eighth in prelims heat number four.

At the 2021 World Swimming Championships conducted in short course metres and held at Etihad Arena in Abu Dhabi, United Arab Emirates, Walshe set a new Irish record in the 400 metre individual medley with a time of 4:30.78 in the prelims heats, which qualified her for the final ranking fourth. In the final of the event, Walshe won the silver medal with a time of 4:26.52, lowering her own Irish record she set in the prelims heats and finishing less than one second after Tessa Cieplucha of Canada. Her silver medal was the second medal won by a swimmer representing Ireland at a World Swimming Championships and the first one won at the championships in an event held at the Olympic Games.

The second day of competition, in the prelims heats of the 200 metre butterfly, Walshe ranked 14th overall with a 2:08.16 and did not qualify for the final. In the prelims heats of the 50 metre butterfly on day three, Walshe placed 22nd with a time of 26.33 seconds, not advancing to the semifinals. On the fifth day, Walshe ranked ninth in the prelims heats of the 200 metre individual medley with a 2:08.69 and achieved alternate status for the final. Her time of 2:08.69 set a new Irish record. Later in the same prelims session, Walshe qualified for the semifinals of the 100 metre butterfly with an Irish record time of 57.32 seconds that tied her in rank for fourteenth with Margaret MacNeil of Canada. In the semifinals of the 100 metre butterfly, Walshe ranked ninth and attained first alternate status for the final with an Irish record time of 56.68 seconds.