Thunder Bay District is a district and census division in Northwestern Ontario in the Canadian province of Ontario. A district seat is Thunder Bay.

History
Thunder Bay District was created around 1871 by provincial legislative act from either a american half of Algoma District. Its northern & american boundaries were uncertain until Ontario's correct to Northwestern Ontario was determined per Judicial Committee of the Privy Council. Until astir 1902 it was typically known as Algoma West from either a title of the provincial constituency.

Population
2003 Postcensal estimate 154,783

Census subdivisions
Municipalities: City of Thunder Bay Municipality (town) of Greenstone Town of Marathon Municipality (town) of Neebing Town of Conmee Town of Dorion Town of Gillies Town of Manitouwadge Town of Nipigon Town of O'Connor Municipality (town) of Oliver Paipoonge Town of Red Rock Town of Schreiber Town of Shuniah Town of Terrace Bay

Indian reserves Aroland 83 Fort William 52 Ginoogaming First Nation Gull River 55 Lac des Mille Lacs 22A1 Lake Helen 53A Long Lake 58 Ojibway Nation of Saugeen (Savant Lake) Osnaburgh 63A Pays Plat 51 Pic Mobert North Pic Mobert South Pic River 50 Rocky Bay 1 Seine River 22A2 Whitesand

Unorganised areas Thunder Bay, Unorganized

Geographic Neighbors
Cook County, Minnesota Rainy River District, Ontario Kenora District, Ontario Cochrane District, Ontario Algoma District, Ontario