A native of Ljubljana, Dončić began his basketball career with the youth teams of Slovenian club Union Olimpija, joining at eight years of age. In 2012, he joined Real Madrid in Spain, eventually rising in profile on the reserve team. At age 16, in the 2014–15 season, Dončić debuted for Real Madrid in both the Liga ACB and EuroLeague, becoming the youngest player in club history to suit up in either competition. He found an increasing presence on the senior team in 2016–17, winning the EuroLeague Rising Star and ACB Best Young Player Award. In the 2017–18 season, Dončić assumed a leading role for Real Madrid, replacing its injured star player Sergio Llull for much of the season. Guiding his team to the 2018 EuroLeague title at age 19, he became the youngest recipient of the EuroLeague MVP and EuroLeague Final Four MVP awards. He was also the youngest player to ever be named ACB Most Valuable Player. In addition, Dončić earned EuroLeague Rising Star and ACB Best Young Player accolades for his second straight season.