An urban agglomeration is defined as "a continuous urban spread constituting a town and its adjoining outgrowths, or two or more physically contiguous towns together with or without outgrowths of such towns". An urban agglomeration must consist of at least a statutory town and its total population (i.e. all the constituents put together) should not be less than 20,000.
Below is a list of urban agglomerations in the state of Tamil Nadu, with a population of 1 lakh and above based on the 2011 census of India.[1] Cities in bold are declared Municipal corporations.
| 1 | Chennai | Chennai | 8,696,010 | |
| 2 | Coimbatore | Coimbatore | 2,151,466 | |
| 3 | Madurai | Madurai | 1,462,420 | |
| 4 | Tiruchirappalli | Tiruchirappalli | 1,021,717 | |
| 5 | Tiruppur | Tiruppur | 962,982 | |
| 6 | Salem | Salem | 919,950 | |
| 7 | Erode | Erode | 521,776 | |
| 8 | Tirunelveli | Tirunelveli | 498,924 | |
| 9 | Vellore | Vellore | 481,966 | |
| 10 | Thoothukudi | Thoothukudi | 410,760 | |
| 11 | Dindigul | Dindigul | 292,132 | |
| 12 | Thanjavur | Thanjavur | 290,724 | |
| 13 | Ranipet | Ranipet district | 262,346 | |
| 14 | Sivakasi | Virudhunagar | 234,688 | |
| 15 | Karur | Karur | 233,763 | |
| 16 | Udhagamandalam | Nilgiris | 233,374 | |
| 17 | Hosur | Krishnagiri | 229,507 | |
| 18 | Nagercoil | Kanyakumari | 224,849 | |
| 19 | Kancheepuram | Kancheepuram | 221,749 | |
| 20 | Komarapalayam | Namakkal | 194,992 | |
| 21 | Karaikudi | Sivaganga | 181,347 | |
| 22 | Neyveli | Cuddalore | 178,925 | |
| 23 | Cuddalore | Cuddalore | 173,361 | |
| 24 | Kumbakonam | Thanjavur | 167,098 | |
| 25 | Tiruvannamalai | Tiruvannamalai | 144,683 | |
| 26 | Pollachi | Coimbatore | 135,235 | |
| 27 | Rajapalayam | Virudhunagar | 130,119 | |
| 28 | Gudiyatham | Vellore | 124,274 | |
| 29 | Pudukottai | Pudukottai | 117,215 | |
| 30 | Vaniyambadi | Tirupattur | 116,712 | |
| 31 | Ambur | Tirupattur | 113,856 | |
| 32 | Nagapattinam | Nagapattinam | 102,838 |