She is the current record holder under the 20-point judging system with the highest All-around total of 77.150 points; which she scored at the 2016 Baku World Cup.

[16] Following the Russian invasion of Ukraine in February 2022, she posted a picture of a blue sky and yellow meadow on Instagram with the caption "The World needs peace!".

She made her senior international breakthrough at the 2011 World Cup in Montreal, Quebec, Canada, where she won the bronze medal in all-around and gold in ball finals ahead of Liubov Charkashyna.

She and teammate Daria Dmitrieva then competed at the senior 2012 AEON Cup in Japan and won the team gold medal.

[citation needed] In 2013, Mamun started her season competing at the Moscow Grand Prix winning the gold medal in all-around ahead of silver medalist Sylvia Miteva and teammate Daria Svatkovskaya.

She won the gold medal in All-around and in all apparatus finals at the second World Cup series event held in Lisbon, Portugal.

[citation needed] Mamun competed at the 2013 World Cup event in Sofia, where she won the bronze in all-around behind Bulgarian Sylvia Miteva.

Mamun won the all-around at the 2013 Grand Prix Final in Berlin and gold medal in hoop and ball, silver in clubs behind Daria Svatkovskaya and 5th in ribbon.

[26] In 2014, Mamun began her competitive season at the 2014 Moscow Grand Prix where she won the all-around gold medal ahead of teammate Maria Titova.

[citation needed] Mamun then competed at the 2014 World Cup series event in Stuttgart, where she won all-around silver.

[citation needed] On 23–27 April, Mamun competed as the defending national champion at the 2014 Russian Championships, where she won the All-around silver medal, behind Kudryavtseva.

On 22–24 May, Mamun won her second World Cup all-around title of the season at Tashkent scoring an overall total of 74.750 points, ahead of teammates Yana Kudryavtseva (silver) and Aleksandra Soldatova (bronze).

[28] In her next event, Mamun won the all-around bronze medal at the Minsk leg of the World Cup series, behind Melitina Staniouta.

On 5–7 September, competing at the 2014 World Cup series in Kazan, Mamun took the all-around silver medal behind Kudryavtseva with a total of 73.250 points.

[31] On 22–28 September, Mamun (along with teammates Yana Kudryavtseva and Aleksandra Soldatova) represented Russia at the 2014 World Championships where they won Team gold with a total of 147.914 points.

She qualified to all event finals and won 2 gold medals in ribbon and ball (tied with Kudryavtseva), 2 silver in hoop, clubs.

[citation needed] On 13–15 March, Mamun won the gold medal at the Trophy de Barcelona in the all-around, (ball, ribbon, clubs) and silver in hoop.

[citation needed] On 1–3 May, Mamun competed at the 2015 European Championships where she together with Yana Kudryavtseva and Aleksandra Soldatova won team gold for Russia.

Mamun swept her first gold for the season at the 2015 Tashkent World Cup, where she won the all-around title with a total of 75.500 points and all 4 event finals.

On 12–28 June, Mamun participated at the inaugural 2015 European Games in Baku, where she won the silver medal in the all-around with a total of 75.650 points (a personal best).

[34] On 9–13 September, at the 2015 World Championships in Stuttgart, Mamun (together with teammates Yana Kudryavtseva and Aleksandra Soldatova) represented Russia, where they won the team gold.

Mamun then competed at the 2015 Grand Prix Final in Brno, where she won the all-around gold medal with a total of 76.050, a personal best score.

[citation needed] In 2016, Mamun started her season at the 2016 Moscow Grand Prix finishing 4th in the all-around, she qualified to 2 apparatus finals taking gold in clubs and ball (tied with teammate Aleksandra Soldatova).

[38] On 1–3 April, Mamun competed at the 2016 Pesaro World Cup where she won the all-around silver with a total of 75.900 points (a new Personal Best) behind teammate Yana Kudryavtseva, she qualified to 3 apparatus finals taking gold in hoop, clubs, placed 5th in ball and 4th in ribbon.

[48] On 4 November 2017, Irina Viner officially announced to the Russian press that Mamun has completed her competitive career in rhythmic gymnastics.