(Click on the column title to sort by that column)
| # | Catholics | Population | Percent Catholic | Diocese | Year | Source |
|---|---|---|---|---|---|---|
| 1 | 3,359,000 | 3,746,000 | 89.67% | Madrid (Archdiocese) | 2004 | ap2005 |
| 2 | 2,484,037 | 2,562,333 | 96.94% | Valencia (Archdiocese) | 2004 | ap2005 |
| 3 | 1,749,750 | 1,758,720 | 99.49% | Sevilla {Seville} (Archdiocese) | 2004 | ap2005 |
| 4 | 1,371,185 | 1,443,353 | 95.00% | Málaga | 2004 | ap2005 |
| 5 | 1,161,590 | 1,290,656 | 90.00% | Getafe | 2004 | ap2005 |
| 6 | 1,155,000 | 1,260,000 | 91.67% | Orihuela-Alicante | 2004 | ap2005 |
| 7 | 1,132,664 | 1,287,118 | 88.00% | Santiago de Compostela (Archdiocese) | 2004 | ap2005 |
| 8 | 1,127,469 | 1,226,993 | 91.89% | Cartagena (en España) | 2004 | ap2005 |
| 9 | 1,016,235 | 1,075,381 | 94.50% | Oviedo (Archdiocese) | 2004 | ap2005 |
| 10 | 1,000,000 | 1,129,805 | 88.51% | Bilbao | 2004 | ap2005 |
| 11 | 1,000,000 | 1,100,000 | 90.91% | Terrassa | 2004 | ap2005 |
| 12 | 832,665 | 979,606 | 85.00% | Islas Canarias {Canary Islands} | 2004 | ap2005 |
| 13 | 823,736 | 915,262 | 90.00% | San Cristóbal de La Laguna o Tenerife | 2004 | ap2005 |
| 14 | 770,000 | 794,000 | 96.98% | Zaragoza (Archdiocese) | 2004 | ap2005 |
| 15 | 768,337 | 771,131 | 99.64% | Córdoba | 2004 | ap2005 |
| 16 | 702,000 | 732,850 | 95.79% | Cádiz y Ceuta | 2004 | ap2005 |
| 17 | 679,845 | 706,896 | 96.17% | Granada (Archdiocese) | 2004 | ap2005 |
| 18 | 630,000 | 651,565 | 96.69% | Jaén | 2004 | ap2005 |
| 19 | 621,988 | 684,416 | 90.88% | San Sebastián | 2004 | ap2005 |
| 20 | 602,289 | 650,789 | 92.55% | Alcalá de Henares | 2004 | ap2005 |
| 21 | 600,000 | 687,314 | 87.30% | Girona | 2004 | ap2005 |
| 22 | 600,000 | 661,393 | 90.72% | Sant Feliu de Llobregat | 2004 | ap2005 |
| 23 | 594,860 | 753,584 | 78.94% | Mallorca | 2004 | ap2005 |
| 24 | 581,414 | 585,290 | 99.34% | Mérida-Badajoz (Archdiocese) | 2004 | ap2005 |
| 25 | 573,386 | 578,210 | 99.17% | Pamplona y Tudela (Archdiocese) | 2004 | ap2005 |
| 26 | 566,538 | 574,409 | 98.63% | Toledo (Archdiocese) | 2004 | ap2005 |
| 27 | 545,937 | 552,727 | 98.77% | Santander | 2004 | ap2005 |
| 28 | 519,503 | 565,310 | 91.90% | Almería | 2004 | ap2005 |
| 29 | 500,000 | 517,658 | 96.59% | Tui-Vigo | 2004 | ap2005 |
| 30 | 483,669 | 487,670 | 99.18% | Ciudad Real | 2004 | ap2005 |
| 31 | 455,672 | 506,302 | 90.00% | Valladolid (Archdiocese) | 2004 | ap2005 |
| 32 | 446,337 | 464,934 | 96.00% | Huelva | 2004 | ap2005 |
| 33 | 445,361 | 500,653 | 88.96% | Jerez de la Frontera | 2004 | ap2005 |
| 34 | 437,000 | 456,526 | 95.72% | Tarragona (Archdiocese) | 2004 | ap2005 |
| 35 | 420,301 | 440,746 | 95.36% | Segorbe-Castellón de la Plana | 2004 | ap2005 |
| 36 | 376,184 | 383,870 | 98.00% | Vic | 2004 | ap2005 |
| 37 | 371,859 | 376,787 | 98.69% | Albacete | 2004 | ap2005 |
| 38 | 337,445 | 355,205 | 95.00% | Burgos (Archdiocese) | 2004 | ap2005 |
| 39 | 314,172 | 315,452 | 99.59% | León | 2004 | ap2005 |
| 40 | 314,107 | 315,407 | 99.59% | Orense | 2004 | ap2005 |
| 41 | 296,389 | 296,961 | 99.81% | Lugo | 2004 | ap2005 |
| 42 | 286,097 | 288,998 | 99.00% | Mondoñedo-Ferrol | 2004 | ap2005 |
| 43 | 278,134 | 302,164 | 92.05% | Vitoria | 2004 | ap2005 |
| 44 | 275,000 | 280,000 | 98.21% | Salamanca | 2004 | ap2005 |
| 45 | 274,540 | 276,810 | 99.18% | Astorga | 2004 | ap2005 |
| 46 | 266,724 | 272,654 | 97.83% | Plasencia | 2004 | ap2005 |
| 47 | 261,715 | 287,000 | 91.19% | Calahorra y La Calzada-Logroño | 2004 | ap2005 |
| 48 | 252,010 | 264,090 | 95.43% | Coria-Cáceres | 2004 | ap2005 |
| 49 | 239,518 | 242,300 | 98.85% | Tortosa | 2004 | ap2005 |
| 50 | 199,722 | 202,982 | 98.39% | Cuenca | 2004 | ap2005 |
| 51 | 192,592 | 196,996 | 97.76% | Lleida | 2004 | ap2005 |
| 52 | 178,537 | 185,474 | 96.26% | Sigüenza-Guadalajara | 2004 | ap2005 |
| 53 | 178,295 | 184,395 | 96.69% | Urgell | 2004 | ap2005 |
| 54 | 174,471 | 177,128 | 98.50% | Palencia | 2004 | ap2005 |
| 55 | 164,228 | 165,428 | 99.27% | Zamora | 2004 | ap2005 |
| 56 | 163,466 | 165,480 | 98.78% | Avila | 2004 | ap2005 |
| 57 | 146,200 | 150,701 | 97.01% | Segovia | 2004 | ap2005 |
| 58 | 107,254 | 109,254 | 98.17% | Guadix | 2004 | ap2005 |
| 59 | 101,521 | 124,071 | 81.82% | Solsona | 2004 | ap2005 |
| 60 | 100,000 | 112,730 | 88.71% | Ibiza | 2004 | ap2005 |
| 61 | 95,000 | 95,887 | 99.07% | Barbastro-Monzón | 2004 | ap2005 |
| 62 | 87,932 | 89,533 | 98.21% | Teruel y Albarracín | 2004 | ap2005 |
| 63 | 80,583 | 83,220 | 96.83% | Tarazona | 2004 | ap2005 |
| 64 | 78,000 | 79,000 | 98.73% | Huesca | 2004 | ap2005 |
| 65 | 76,000 | 81,288 | 93.49% | Menorca | 2004 | ap2005 |
| 66 | 73,190 | 91,487 | 80.00% | Osma-Soria | 2004 | ap2005 |
| 67 | 46,442 | 46,780 | 99.28% | Jaca | 2004 | ap2005 |
| 68 | 44,587 | 45,614 | 97.75% | Ciudad Rodrigo | 2004 | ap2005 |
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