| City | County | 2026 Pop. ↓ |
|---|---|---|
| Lowell | Middlesex County | 119,847 |
| Lynn | Essex County | 104,710 |
| Lawrence | Essex County | 89,147 |
| Leominster | Worcester County | 44,134 |
| Lexington | Middlesex County | 34,694 |
| Ludlow | Hampden County | 21,467 |
| Longmeadow | Hampden County | 15,688 |
| Lynnfield | Essex County | 13,296 |
| Lakeville | Plymouth County | 12,545 |
| Lunenburg | Worcester County | 12,058 |
| Leicester | Worcester County | 11,434 |
| Littleton | Middlesex County | 10,395 |
| Lancaster | Worcester County | 9,296 |
| Lincoln | Middlesex County | 6,912 |
| Lee | Berkshire County | 5,649 |
| Lenox | Berkshire County | 5,037 |
| Lanesborough | Berkshire County | 2,979 |
| Leverett | Franklin County | 1,843 |
| Leyden | Franklin County | 722 |