San Diego County, San Diego County, founded in 1850, is one of 58 counties in the US state of California. In 2010 census, the county had a population of 3,222,466 and a population density of 275 people per km², making it the fifth most populous county in the United States and the second in California. In 2019 county had a population of 3,338,330.. The county's headquarters are San Diego.. San Diego County has a population of 3,332,427.
There are 15 countries in Europe with a population smaller than San Diego County.
| # | Country | Capital City | Population |
| 1 | Vatican | Vatican City | 0 |
| 2 | Monaco | Monaco | 0 |
| 3 | Gibraltar | Gibraltar | 0 |
| 4 | San Marino | San Marino | 0 |
| 5 | Guernsey | St Peter Port | 0 |
| 6 | Jersey | Saint Helier | 0 |
| 7 | Liechtenstein | Vaduz | 0 |
| 8 | Malta | Valletta | 0 |
| 9 | Andorra | Andorra la Vella | 0 |
| 10 | Isle of Man | Douglas | 0 |
| 11 | Faroe Islands | Torshavn | 0 |
| 12 | Aland Islands | Mariehamn | 0 |
| 13 | Luxembourg | Luxembourg | 0 |
| 14 | Cyprus | Nicosia | 0 |
| 15 | Kosovo | Pristina | 0 |
There are 11 countries in Asia with a population smaller than San Diego County.
| # | Country | Capital City | Population |
| 1 | Cocos Islands | West Island | 0 |
| 2 | British Indian Ocean Territory | Diego Garcia | 0 |
| 3 | Macao | Macao | 0 |
| 4 | Maldives | Male | 0 |
| 5 | Bahrain | Manama | 0 |
| 6 | Singapore | Singapore | 0 |
| 7 | Hong Kong | Hong Kong | 0 |
| 8 | Brunei | Bandar Seri Begawan | 0 |
| 9 | Palestinian Territory | East Jerusalem | 0 |
| 10 | Lebanon | Beirut | 0 |
| 11 | Qatar | Doha | 0 |
There are 0 countries in South America with a population smaller than San Diego County.
| # | Country | Capital City | Population |
There are 20 countries in Ocenia with a population smaller than San Diego County.
| # | Country | Capital City | Population |
| 1 | United States Minor Outlying Islands | 0 | |
| 2 | Tokelau | 0 | |
| 3 | Nauru | Yaren | 0 |
| 4 | Tuvalu | Funafuti | 0 |
| 5 | Norfolk Island | Kingston | 0 |
| 6 | Pitcairn | Adamstown | 0 |
| 7 | Christmas Island | Flying Fish Cove | 0 |
| 8 | Marshall Islands | Majuro | 0 |
| 9 | American Samoa | Pago Pago | 0 |
| 10 | Cook Islands | Avarua | 0 |
| 11 | Niue | Alofi | 0 |
| 12 | Wallis and Futuna | Mata Utu | 0 |
| 13 | Palau | Melekeok | 0 |
| 14 | Northern Mariana Islands | Saipan | 0 |
| 15 | Guam | Hagatna | 0 |
| 16 | Micronesia | Palikir | 0 |
| 17 | Tonga | Nuku'alofa | 0 |
| 18 | Kiribati | Tarawa | 0 |
| 19 | Samoa | Apia | 0 |
| 20 | French Polynesia | Papeete | 0 |
