FC Andorra - owned by Barcelona defender Gerard Pique - have paid 452,022 euros (£411,000) to fill a vacated slot in Spain's third tier.
The club, bought by Pique's Kosmos group in December, earned promotion to the fourth tier last season but have now replaced Reus, who were relegated as a result of financial problems.
Zamora, Jaen, Intercity and Linares were also keen on replacing Reus.
FC Andorra, founded in 1942, have played in the league system since 1948.
When Kosmos took charge of the club, they were struggling with debt in the fifth-tier Primera Catalana regional division, one point off the relegation places and 17 points behind the leaders.
The fee paid by Andorra was a requirement of the Royal Spanish Football Federation (RFEF).