Admission to Danish state-owned or state-approved museums and collections under the Ministry of Culture is free for children and adolescents under 18 years.

Admission to the National Museum and Statens Museum for Kunst (both Copenhagen) is free for everybody, although entrance to special exhibitions in some cases may be charged.

A few museums and collections offer free admission once a week (normally Wednesdays) to everybody, although entrance to special exhibitions in some cases may be charged also on the day of free admission.

The museums with free admission for everybody once a week are:
Ny Carlsberg Glyptotek, Copenhagen (Sun)
Tøjhusmuseet (Museum of Arms and Uniforms), Copenhagen (Weds)
Jagt- og Skovbrugsmuseet (Hunting and Forestry Museum), Hørsholm (Weds)
Post & Tele Museum, Copenhagen (all days) 
Orlogsmuseet (Naval Museum), Copenhagen (Weds)
Thorvaldsens Museum, Copenhagen (Weds)
Københavns Bymuseum (Museum of City of Copenhagen), Copenhagen (Fri)
Designmuseet Danmark, Copenhagen (Weds)
Dansk Landbrugsmuseum (Museum of Danish Agriculture), Gl. Estrup, Randers (Fri)

Read more about museums in Denmark