Mariagerfjord Municipality (Danish: Mariagerfjord Kommune) is a municipality (Danish, kommune) in North Jutland Region in Denmark. It covers an area of 723.63 km²; (2011) it has a population of 41,762 (2024).

On 1 January 2007 Mariagerfjord municipality was created as the result of Kommunalreformen ("The Municipal Reform" of 2007), consisting of the former municipalities of Arden, Hadsund and Hobro, and the major part of Mariager, and a very small part of Aalestrup and a very small part of Nørager municipality.

The municipality consists of the land around Mariager Fjord, its namesake.

Hobro	12,000
Hadsund	5,000
Mariager	2,500
Arden	2,500
Assens	1,400
Valsgård	1,100
Als	900
Øster Hurup	700
Astrup	500

Mariagerfjord's municipal council consists of 29 members, elected every four years.

Below are the municipal councils elected since the Municipal Reform of 2007.

Election	Party								Total seats	Turnout	Elected mayor
	A	B	C	D	F	I	O	V
2005	13	1	1		1		1	12	29	72.6%	Hans Christian Maarup (A)
2009	13		1	1	2		2	10		68.2%
2013	13				1	1	3	11		72.8%	Mogens Jespersen (V)
2017	11	1	1		1		3	12		71.1%
Data from Kmdvalg.dk 2005, 2009, 2013 and 2017

• Municipal statistics: NetBorger Kommunefakta, delivered from KMD aka Kommunedata (Municipal Data)
• Municipal mergers and neighbors: Eniro new municipalities map

• Mariagerfjord municipality's official website (in Danish)
• Municipal Key Figures - area