| Official Name: | Mill Bay, Alaska |
| Settlement Type: | Census-designated place |
| Pushpin Map: | Alaska#North America |
| Pushpin Label: | Mill Bay |
| Pushpin Label Position: | right |
| Subdivision Type: | Country |
| Subdivision Name: | United States |
| Subdivision Type1: | State |
| Subdivision Name1: | Alaska |
| Subdivision Type2: | Borough |
| Subdivision Name2: | Kodiak Island |
| Leader Title: | Borough mayor |
| Leader Name: | Aimee Williams |
| Leader Title1: | State senator |
| Leader Name1: | Gary Stevens (R) |
| Leader Title2: | State rep. |
| Leader Name2: | Louise Stutes (R) |
| Area Footnotes: | [1] |
| Area Total Km2: | 9.35 |
| Area Land Km2: | 8.92 |
| Area Water Km2: | 0.43 |
| Area Total Sq Mi: | 3.61 |
| Area Land Sq Mi: | 3.44 |
| Area Water Sq Mi: | 0.17 |
| Population As Of: | 2020 |
| Population Total: | 4216 |
| Population Density Km2: | 472.71 |
| Population Density Sq Mi: | 1224.16 |
| Timezone: | Alaska (AKST) |
| Utc Offset: | -9 |
| Timezone Dst: | AKDT |
| Utc Offset Dst: | -8 |
| Elevation Ft: | 20 |
| Coordinates: | 57.8211°N -152.3547°W |
| Postal Code Type: | ZIP code |
| Postal Code: | 99615[2] |
| Area Code: | 907 |
| Blank Name: | FIPS code |
| Blank Info: | 02-49200 |
| Unit Pref: | Imperial |
Mill Bay is a census-designated place (CDP) in Kodiak Island Borough, Alaska, United States. It was first listed as a CDP prior to the 2020 census.
Mill Bay is located at the northeast tip of Kodiak Island, surrounding the small bay for which the community is named. It is bordered to the southwest by the city of Kodiak.
According to the United States Census Bureau, the Mill Bay CDP has a total area of 9.35km2, of which 8.92km2 are land and 0.43km2, or 4.62%, are water.
As of the 2020 census, the population of the CDP is 4,216.[3] It is the second most populated place in the borough.