The hotel chain is initially looking at 15 premises across the country, including in the Canaries and Balearics.
All hotels will follow new health and safety protocols to meet new Covid challenges.
Riu is gradually restarting its operations globally, with 50 hotels across 15 countries either open or ready to resume operations.
It comes as Spain prepares to reopen its borders to overseas tourists on Sunday (21 June).
The first 15 Riu hotels to reopen are situated in Madrid, Majorca, Formentera, Cadiz, Malaga, Gran Canaria, Tenerife, Fuerteventura and Lanzarote.
Riu Bravo and Riu Concordia in Palma will be first, with Riu working with Tui and the Balearic government to support the island’s safe tourism test which got under way on Monday (15 June).
In the Canaries, the first hotel to welcome back guests will be Riu Gran Canaria on 19 June; two of the chain’s hotels in Andalusia, Riu Chiclana and Riu Costa del Sol, as well as Riu La Mola in Playa de Migjorn on Formentera, will open the same day.
Riu Palace Meloneras in Gran Canaria and Riu Palace Tres in Fuerteventura will follow on 26 June; Riu Calypso Hotel (Fuerteventura) and Riu Paraiso Lanzarote on 1 July; and Riu Palaca Tenerife on 2 July.
Riu Palace Palmeras (Gran Canaria), Riu Arecas (Tenerife) and Riu Nautilus (Torremolinos) will follow "shortly after".
Operations have resumed in 15 other countries, with hotels open or ready to open in Germany, Mexico, the US, Bulgaria, Portugal, Ireland, Jamaica, Costa Rica, Aruba, the Dominican Republic, the Bahamas, Morocco, Zanzibar and Sri Lanka.
All hotels will a new set of 17 strict health and safety protocols, agreed with consultant Preverisk. Riu has developed new training for staff on the measures, while hotel occupancy will be initially limited to 50% or 60% unless national restrictions deem otherwise.
The chain this week announced it would offer all guests up to €30,000 Covid medical cover should their stay be impacted by coronavirus.
