Even though the club registered with the Royal Spanish Football Federation on 6 June 1949, UD Las Palmas was officially founded on 22 August of that year, as the result of a merger between all five clubs on the island: Club Deportivo Gran Canaria, Atlético Club de Fútbol, Real Club Victoria, Arenas Club and Marino Fútbol Club. The union was to create a club strong enough to keep Canarian players on the island and not to seek a better career on the mainland.
Debate was held on the name of the club, which it was agreed would not include the names of any of its predecessors. An early option, Deportivo Canarias, was scrapped due to referring to the Canary Islands on a whole rather than the island of Gran Canaria. The name Las Palmas by itself was also put forward, and then rejected due to the name having already been taken by a defunct club in the city; Unión Deportiva Las Palmas was finally chosen due to its connection to the union which created the team, and its home city of Las Palmas. The first training session at the new club was held on 16 September 1949.
Las Palmas finished second in their first season in the Tercera División (1949–50), ranking third in the following year’s Segunda División to reach La Liga for the first time ever, and became the first Spanish club to achieve consecutive promotions in its first two years of existence. The first season in the top flight ended, however, in relegation, but the team returned to the category in 1954, going on to enjoy a six-year spell.