| Allan Water | |
| Name Etymology: | Named after Allan Water in Scotland |
| Pushpin Map: | Canada Ontario |
| Pushpin Map Caption: | Location of the mouth of the Allan Water in Ontario |
| Subdivision Type1: | Country |
| Subdivision Name1: | Canada |
| Subdivision Type2: | Province |
| Subdivision Name2: | Ontario |
| Subdivision Type3: | Region |
| Subdivision Name3: | Northwestern Ontario |
| Subdivision Type4: | District |
| Subdivision Name4: | Thunder Bay |
| Subdivision Type5: | Part |
| Subdivision Name5: | Thunder Bay, Unorganized |
| Length: | 71km (44miles) |
| Source1: | Kawaweogama Lake |
| Source1 Location: | Allanwater Bridge |
| Source1 Coordinates: | 50.2417°N -90.1639°W |
| Source1 Elevation: | 417m (1,368feet) |
| Mouth: | Wabakimi Lake |
| Mouth Coordinates: | 50.6203°N -89.7392°W |
| Mouth Elevation: | 357m (1,171feet) |
| River System: | James Bay drainage basin |
Allan Water is a river in the James Bay drainage basin in Unorganized Thunder Bay District in northwestern Ontario, Canada.
The river begins at the community of Allanwater Bridge at the confluence of the two branches of the Brightsand River: the western branch arriving as the outlet from Kawaweogama Lake and the eastern branch arriving as the outlet from McEwan Lake. The Canadian National Railway Canadian National Railway transcontinental main line over a bridge at the point of confluence, and is the location of Allanwater Bridge railway station, served by Via Rail transcontinental Canadian trains.
The river flows north and splits into two channels, then recombines, takes in the right tributary Nemo River and reaches Brennan Lake. The river leaves the lake east over Brennan Falls to Granite Lake, and then leaves that lake north over Granite Falls. It continues north over Black Beaver Rapids, Little Sturgeon Rapids and Sturgeon Rapids to reach its mouth at Wabakimi Lake on the Ogoki River. The Ogoki flows via the Albany River to James Bay.
With the exception of a short stretch at the start, the river lies within Wabakimi Provincial Park.