Real Madrid on Thursday formally introduced Franco Mastantuono after completing a transfer worth about €63 million from River Plate, the most expensive outgoing deal in Argentine football history. The 18-year-old, who turned 18 the same day, signed a contract that ties him to the European champions until June 2031 and will wear the rarely used No. 30 shirt. After passing his medical in the morning, the left-footed attacking midfielder stood alongside club president Florentino Pérez at Valdebebas and declared, “I’m living a dream. I promise to give my life for this team.” Asked to name the world’s best player, the Argentine chose compatriot Lionel Messi, a nod that surprised some Madrid supporters but drew no rebuke from the club. To avoid filling its 25-man LaLiga quota, Real Madrid has provisionally registered Mastantuono with its reserve side, Castilla, leaving one senior roster spot open for potential late-summer business. The move does not affect his availability for the first team once coach Xabi Alonso deems him ready. Mastantuono will join his new teammates in training later this week. Club officials said his competitive debut could come as early as the league fixture against Osasuna on 19 August, or in subsequent matches against Real Oviedo and Mallorca.