The 21-year-old has been included in the set-up for the forthcoming European Championship qualifiers on the back of an impressive display in Town's 3-0 win over Crystal Palace last weekend.
It is the first time the midfielder has been selected as the young Danes look to qualify for the 2019 Under 21 European Championships in Italy.
The side will face the Faroe Islands in their opening match of the qualifiers on Thursday August 31 (4pm kick-off UK time) at Tórsvøllur Stadium in Torshavn.
They then face Lithuania on Tuesday September 5 at the Aalborg Stadion in Aalborg (once again a 4pm kick-off UK time).
Speaking on the call-up, Billing said: “I'm delighted – it's always a privilege to play for your country and this shows the work I am doing at Huddersfield Town is paying off.
“Playing for your country is something you dream of as a kid and I'm hoping to show everyone what I am capable of.
“Appearing for the first-team is obviously the dream but I've just got to keep working hard and that will come one day.
“For now I am just concentrating on the Under 21s and taking it from there."