Maria-Chapdelaine is a regional county municipality in the Saguenay–Lac-Saint-Jean region of Quebec, Canada. Its seat is in Dolbeau-Mistassini.

It runs from Lac Saint-Jean in the south to the deep interior of northern Quebec in the north.

There are 14 subdivisions within the RCM:

Highways and numbered routes that run through the municipality, including external routes that start or finish at the county border:

In the 2021 Census of Population conducted by Statistics Canada, the RCM of Maria-Chapdelaine had a population of 24,149 living in 10,967 of its 12,185 total private dwellings, a change of -2.6% from its 2016 population of 24,793. With a land area of 35,501.49 km (13,707.20 sq mi), it had a population density of 0.7/km (1.8/sq mi) in 2021.

In 2021, the median age was 50.0, as opposed to 41.6 for all of Canada. French was the mother tongue of 99.0% of residents in 2021. The next most common mother tongues were the related languages of Atikamekw and Innu at 0.3% total, followed by English and Spanish at 0.3% each. 0.3% reported both English and French as their first language. Additionally there were 0.1% who reported both French and a non-official language as their mother tongue.

As of 2021, Indigenous peoples comprised 6.8% of the population, and visible minorities contributed 1.1%. The largest visible minority groups in the RCM of Maria-Chapdelaine are Black (0.5%), Arab (0.2%), and Latin American (0.2%).

In 2021, 79.1% of the population identified as Catholic, while 13.6% said they had no religious affiliation. Jehovah's Witnesses were the largest religious minority, making up 0.6% of the population. Muslims were the largest non-Christian religious minority, making up just over 0.1% of the population.

Counting both single and multiple responses, the most commonly identified ethnocultural ancestries were:

Ethnic origin	2021
Canadian	42.1%
French	21.0%
Québécois	15.4%
French Canadian	9.4%
First Nations	4.2%
Métis	2.7%
Irish	1.6%
Innu	1.2%
Acadian	1.0%

(Percentages may total more than 100% due to rounding and multiple responses).

• List of regional county municipalities and equivalent territories in Quebec