Demir Kapija (Macedonian: Демир Капија [ˌdɛmir ˈkapija] ) is a municipality in southern part of North Macedonia. Demir Kapija, which means "iron door" or "iron gate" in Turkish, is also the name of the town where the municipal seat is found. Demir Kapija Municipality is part of the Vardar Statistical Region.

The Došnica river which springs from Mount Kožuf is the source of drinking water and hydroelectric power production (at Čiflik) for the municipality.

The municipality borders

• Negotino Municipality to the northwest,
• Konče Municipality to the northeast,
• Valandovo Municipality to the east,
• Gevgelija Municipality to the southeast, and
• Kavadarci Municipality to the southwest.

According to the last national census from 2021 this municipality has 3,777 inhabitants.

Ethnic groups in the municipality include:

	2002		2021
	Number	%	Number	%
TOTAL	4,545	100	3,777	100
Macedonians	3,997	87.9	3,076	81.44
Turks	344	7.6	376	9.95
Serbs	132	2.9	130	3.44
others	72	1.6	80	2.12
Persons for whom data are taken from administrative sources	n/a	n/a	115	3.04

Populated settlements include:

• Demir Kapija (seat)
• Barovo
• Besvica
• Bistrenci
• Čelevec
• Čiflik
• Dračevica
• Dren
• Iberli
• Klisura
• Košarka
• Koprišnica
• Korešnica
• Prždevo
• Strmaševo