Naorem Mahesh Singh is an Indian professional footballer known for his role as a winger. He currently represents the Indian Super League club East Bengal and the Indian national team. Known for his proficiency with his left foot, he sports the jersey number 29. He began his football career with Birchandra Memorial Sporting Club in his home state of Manipur. He later joined the youth side of Shillong Lajong, playing for the club in the Shillong Premier, Previously, he has also been associated with clubs such as Kerala Blasters Football Club, Sudeva Delhi FC, and Royal Wahingdoh FC. Singh primarily plays as a left midfielder (LM) for East Bengal.

Prior to the 2018–19 season, Singh was promoted to the first team of Shillong Lajong. He made his professional debut for Shillong Lajong on 28 October 2018 against Aizawl. He scored two goals in the 20th and 51st minutes as Shillong Lajong won 2–1.

In 2018, it was announced that Singh had signed for the Indian Super League club Kerala Blasters from Shillong Lajong F.C. He was part of the Reserve squad of Kerala Blasters. He never made an appearance for the first team and was loaned out to different clubs during his stint at Blasters. With Kerala Blasters B, he won the Kerala Premier League in 2019–20.

In 2021, Singh was loaned to the I-League side Sudeva Delhi for a season-long deal. He made 14 appearances and scored two goals for the club.

Singh was then loaned to Kolkata-based club East Bengal in 2021. He made 18 appearances and scored two goals for them in the 2021–22 Indian Super League season.

On 4 August 2022, Kerala Blasters announced the transfer of Singh to East Bengal for an undisclosed transfer fee. He scored against Odisha on 18 November 2022 in a 2–4 loss for East Bengal. On 27 November 2022, he became the first Indian player to get three assists in a single Indian Super League game against Jamshedpur, winning the Emerging Player of the Month award. He scored again on 19 February 2023, against Mumbai City in a 1–0 win for East Bengal.

In the 2023–24 season, Singh became the runner-up in the 2023 Durand Cup with East Bengal. On 23 September 2023, it was announced that he had signed a three-year extension with East Bengal till 2027.

On the international stage, Singh was named among the eleven reserves for the Indian senior squad for the 2023 Hero Tri-Nation International Football Tournament, which India won. He was called up to the Indian senior camp for the first time on 14 March 2023, replacing the injured Sivasakthi Narayanan. Singh made his international debut against Myanmar on 22 March 2023, replacing Lallianzuala Chhangte after 70 minutes in a 1–0 victory. As of 2024, he has earned 13 caps and scored 2 international goals for India.

Singh scored his first international goal against Nepal on 24 June 2023 in a 2–0 victory at the 2023 SAFF Championship, which India also won. He scored his second international goal against Iraq on 7 September 2023 in a 2(4)–2(5) semi-final loss at the 2023 King's Cup. His third international goal came against Malaysia on 13 October 2023 in a 2–4 loss in the semi-final of the 2023 Merdeka Tournament.

Singh also won the 2023 Intercontinental Cup with the Indian national team.

Mahesh contributed significantly to East Bengal's victory in the 2024 Indian Super Cup. He had just returned from representing the national team when he played a crucial role in the final match. During the final against Odisha, Mahesh provided an assist for Nandhakumar Sekar, helping East Bengal secure a 3-2 win. This victory marked the end of a twelve-year drought for East Bengal, bringing home a major domestic trophy for the club.

In May 2024, Singh signed a three-year contract extension with East Bengal FC, keeping him at the club until May 2027.