| Mira Sagres Hotel Algarve | 3.0 star rating | 21 | Sagres |
 | Monaco Hotel Algarve | 3.0 star rating | 88 | Faro |
 | Monchique Residences Hotel Algarve | 5.0 star rating | 51 | Monchique |
 | Monica Isabel Beach Club Hotel Algarve | 3.0 star rating | 200 | Albufeira |
 | Monte Carvoeiro Hotel Algarve | 3.0 star rating | 137 | Carvoeiro |
 | Montechoro Hotel Algarve | 4.0 star rating | 362 | Albufeira |
 | Montechoro Clube 99 Hotel Algarve | 3.0 star rating | 47 | Albufeira |
| Monte da Lua Hotel Algarve | Boutique | 6 | Faro |
 | Monte da Quinta Club Hotel Algarve | 4.0 star rating | 178 | Quinta do Lago |
 | Monte da Quinta Resort Algarve | 5.0 star rating | 132 | Quinta do Lago |
 | Monte da Quinta Suites Hotel Algarve | 4.0 star rating | 178 | Quinta do Lago |
| Monte da Vilarinha Hotel Algarve | Rural Hotel | 10 | Aljezur |
 | Monte dos Avos Hotel Algarve | 2.0 star rating | 17 | Tavira |
 | Monte dos Avos Hotel Algarve | 3.0 star rating | 2 | Albufeira |
 | Monte Dourado Hotel Algarve | 3.0 star rating | 109 | Carvoeiro |
 | Montegordo Hotel Apartamentos & Spa Algarve | 4.0 star rating | 86 | Montegordo |
 | Montemar Hotel Algarve | 3.0 star rating | 65 | Lagos |
 | Monte Rei Golf & Country Club Hotel Algarve | Resort | 21 | Altura |
 | Monte Santo Resort Algarve | 5.0 star rating | 133 | Carvoeiro |
 | Montinho de Ouro Hotel Algarve | 4.0 star rating | 6 | Praia da Luz |
 | Morgado Golf and Country Hotel Algarve | 4.0 star rating | 98 | Reguengo |
 | Mouragolf Village Hotel Algarve | 3.0 star rating | 18 | Vilamoura |
 | Mouraliz Apartamentos Hotel Algarve | 3.0 star rating | 24 | Vilamoura |
 | Muthu Clube Praia da Oura Hotel Algarve | Aparthotel 4* | 561 | Albufeira |
 | Muthu Forte da Oura Hotel Algarve | Aparthotel 4* | 115 | Albufeira |
 | Muthu Oura Praia Hotel Algarve | 4.0 star rating | 126 | Albufeira |
 | Natura Algarve Club Hotel | Aparthotel 3* | 63 | Albufeira |
 | Navegadores Hotel Algarve | 3.0 star rating | 346 | Montegordo |
 | Navigator Hotel Algarve | 3.0 star rating | 55 | Sagres |
 | Neptuno Hotel Algarve | 3.0 star rating | 32 | Albufeira |
 | Noria Velha Hotel Algarve | 3.0 star rating | 34 | Carvoeiro |
 | Novochoro Hotel Algarve | 3.0 star rating | 31 | Albufeira |
 | Oasis Beach Apartments Hotel Algarve | Aparthotel 3* | 25 | Praia da Luz |
 | Oceano Atlantico-Apartamentos Turisticos Hotel Algarve | 4.0 star rating | 130 | Praia da Rocha |
 | Oceanus Hotel Algarve | 3.0 star rating | 102 | Albufeira |
 | Ocean View Residences Hotel Algarve | 3.0 star rating | 27 | Albufeira |
 | Olhos D'Agua Hotel Algarve | 3.0 star rating | 41 | Albufeira |
 | Olhos Do Mar Hotel Algarve | 3.0 star rating | 40 | Albufeira |
| OLYMPIAN GOLF APARTMENTS Hotel Algarve | Without Official Category | | Vilamoura |
 | Ondamar Hotel Algarve | 3.0 star rating | | Albufeira |
 | Ondamar Hotel Algarve | 4.0 star rating | 92 | Albufeira |
 | Onyria Palmares Beach House Hotel Algarve | 5.0 star rating | 20 | Lagos |
 | Orada - Marina Albufeira Hotel Algarve | 4.0 star rating | 220 | Albufeira |
 | Orbitur Sagres Hotel Algarve | 1st Camping | 2 | Sagres |
 | Orbitur Valverde Hotel Algarve | 1st Camping | 3 | Lagos |
| Oriental Hotel Algarve | 4.0 star rating | 90 | Praia da Rocha |
| Orquidea Aparhotel Hotel Algarve | 3.0 star rating | | Sagres |
 | Ourabay Hotel Apartamento - Art & Holidays Algarve | 3.0 star rating | 60 | Albufeira |
 | Ourasol Hotel Algarve | 3.0 star rating | 60 | Albufeira |
 | Ouratlantico Hotel Algarve | 3.0 star rating | 74 | Albufeira |