MARC Guiu scored the winner 33 seconds into his senior debut to give Barcelona a 1-0 home win over Athletic Bilbao.
The 17-year-old Spanish forward came on for fellow youngster Fermin Lopez in the 79th minute and struck almost immediately.
It means he has scored his first league goal for Barcelona quicker than any other player in the club’s history.
Victory took third-placed Barca back within a point of leaders Real Madrid, who they face next Saturday.
Barcelona manager Xavi said: “I told him he would have one good chance. I love seeing the face of these kids. They have no fear.”
Earlier on Sunday, Girona won 5-2 at home to Almeria to go level with Real, who drew 1-1 at Sevilla on Saturday.
Guiu was added to Barca’s senior squad as coach Xavi has several players out through injury, including Robert Lewandowski and Frenkie de Jong.
A Joao Felix shot clipped the top of the crossbar from a Ferran Torres cut-back in the first half while Nico Williams had a shot saved by home goalkeeper Marc-Andre ter Stegen.
Just before the hour mark, visiting keeper Unai Simon saved Felix’s low striker before denying Lopez from the rebound.
Then 16-year-old winger Lamine Yamal, who became the youngest scorer in La Liga history earlier this month, dragged a shot wide before fellow substitute Guiu slotted the ball past Simon after being played in by Felix.
Guiu joined Barcelona’s youth academy, more commonly known as La Masia, in 2013.
With Argentina superstar Lionel Messi its most famous product, La Masia’s other graduates include current Barca coach Xavi, Andres Iniesta and Carles Puyol, along with Gerard Pique, Sergio Busquets and Jordi Alba.
Cesc Fabregas left La Masia at 16 to join Arsenal, while Manchester City boss Pep Guardiola is another notable member of La Masia alumni.