36 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Aux Sable township | 1 | 16,105 | 15,373 | 0.95% | 554 | 29.09 | Township |
| Morris | 2 | 14,705 | 14,212 | 0.68% | 1,187 | 12.39 | City |
| Minooka | 3 | 12,958 | 12,760 | 0.31% | 1,380 | 9.39 | Village |
| Morris township | 4 | 7,371 | 7,130 | 0.72% | 2,117 | 3.48 | Township |
| Saratoga township | 5 | 6,646 | 6,402 | 0.82% | 185 | 36 | Township |
| Braceville township | 6 | 6,641 | 6,448 | 0.68% | 372 | 17.87 | Township |
| Coal City | 7 | 5,842 | 5,697 | 0.5% | 1,013 | 5.77 | Village |
| Felix township | 8 | 4,568 | 4,413 | 0.82% | 419 | 10.91 | Township |
| Gardner township | 9 | 4,533 | 4,646 | -0.42% | 107 | 42.56 | Township |
| Diamond | 10 | 2,718 | 2,627 | 0.67% | 1,431 | 1.90 | Village |
| Erienna township | 11 | 2,511 | 2,421 | 0.8% | 121 | 20.82 | Township |
| Wauponsee township | 12 | 2,373 | 2,305 | 0.72% | 89 | 26.79 | Township |
| Goose Lake township | 13 | 1,807 | 1,750 | 0.78% | 73 | 24.91 | Township |
| Mazon township | 14 | 1,496 | 1,470 | 0.54% | 43 | 35.12 | Township |
| Garfield township | 15 | 1,466 | 1,445 | 0.55% | 81 | 18.11 | Township |
| Gardner | 16 | 1,366 | 1,358 | 0.15% | 469 | 2.91 | Village |
| Mazon | 17 | 981 | 978 | 0.1% | 1,630 | 0.60 | Village |
| Braceville | 18 | 724 | 721 | 0.14% | 233 | 3.11 | Village |
| South Wilmington | 19 | 723 | 705 | 0.56% | 1,470 | 0.49 | Village |
| Godley | 20 | 667 | 572 | 2.93% | 616 | 1.08 | Village |
| Rest Haven | 21 | 624 | 550 | 7.22% | 912 | 0.68 | CDP |
| Custer Park | 22 | 555 | 497 | 7.14% | 3,535 | 0.16 | CDP |
| Nettle Creek township | 23 | 489 | 471 | 1.03% | 14 | 35.79 | Township |
| Carbon Hill | 24 | 386 | 375 | 0.52% | 2,121 | 0.18 | Village |
| Lakewood Shores | 25 | 351 | 566 | -15.83% | 1,009 | 0.35 | CDP |
| Goodfarm township | 26 | 351 | 342 | 0.57% | 10 | 35.62 | Township |
| Norman township | 27 | 340 | 325 | 1.19% | 20 | 16.71 | Township |
| Maine township | 28 | 317 | 308 | 0.63% | 18 | 17.89 | Township |
| Lisbon | 29 | 277 | 271 | 0.36% | 131 | 2.12 | Village |
| Plattville | 30 | 224 | 219 | 0.45% | 99 | 2.26 | Village |
| Verona | 31 | 212 | 206 | 0.47% | 1,285 | 0.17 | Village |
| Ritchie | 32 | 193 | 164 | 7.22% | 187 | 1.03 | CDP |
| Symerton | 33 | 122 | 126 | -0.81% | 777 | 0.16 | Village |
| Kinsman | 34 | 90 | 90 | 0% | 1,324 | 0.07 | Village |
| East Brooklyn | 35 | 83 | 80 | 1.22% | 1,596 | 0.05 | Village |
| Lorenzo | 36 | 75 | 31 | 7.14% | 243 | 0.31 | CDP |
Aux Sable township is the largest city in Grundy County, with a population of 16,105.
Lorenzo is the smallest city in Grundy County.
There are 36 cities in Grundy County, Illinois.