Íñigo Sainz-Maza Serna (born 16 June 1998) is a Spanish professional footballer who plays as either a right back or a midfielder for Racing de Santander. Born in Ampuero, Cantabria, Sainz-Maza was a Racing de Santander youth graduate. He made his senior debut with the reserves on 21 February 2016, playing the last eight minutes in a 3–0 Tercera División away win over SD Gama. Sainz-Maza scored his first senior goal on 21 October 2017, netting the opener in a 1–1 home draw against SD Solares-Medio Cudeyo. He made his first team debut on 19 May 2019, starting in a 2–2 home draw against UD Logroñés in the Segunda División B, as his club was already qualified to the play-offs. On 20 August 2020, after Racing's relegation, Sainz-Maza signed his first professional contract with the club and was promoted to the main squad. He was a regular starter for the club during the 2021–22 campaign, scoring once and acting as team captain as his side achieved promotion back to Segunda División. Sainz-Maza made his professional debut on 14 August 2022, starting in a 2–0 away loss against Villarreal CF B. Three days later, he renewed his contract until 2026.