People often draw broad conclusions about people and places from watching movies and TV shows. Stereotypes of Scandinavians and Vikings abound in visual media but separated by the mists of time, the relations between the two people have become hazy.
So, are all Scandinavians descendants of the Vikings?
Many Scandinavians have some Viking ancestry. However, it is difficult to trace what percentage of Viking ancestry every Scandinavian person has or draw the line between who is Scandinavian and who isn’t, making it impossible to answer the question meaningfully.
This article will explain the meanings of the terms Scandinavian and Viking and show why this question doesn’t have a straightforward answer.
Also, see Did Vikings Perform Human Sacrifices? to learn more.
Do Scandinavians Consider Themselves Vikings?
As explained elsewhere on this site, Scandinavian people don’t consider themselves Vikings. 
While Scandinavian culture draws on the Norse heritage of the Viking age, and many of their people share at least some ancestry with these groups, there are several reasons why it is wrong to conflate Vikings and Scandinavians.
Vikings Constituted a Cultural and Not a Genetic or Ethnic Group
Many Vikings did come from the Scandinavian countries—Sweden, Denmark, and Norway. They were a Norse people whose legacy is evident in Scandinavian culture today.
However, this does not necessarily mean that all Scandinavians descended from Vikings.
The terms Norse and Viking were not synonymous, even in their day. That is because while Vikings originated out of Norse culture, not all Norse people of the Viking Age were Vikings.
The term Viking only referred to a specific sub-group of Norse people, who, between the 8th and 11th centuries, voyaged around the world, looting and pillaging.
It is not precisely clear why the Norse resorted to piracy. Some historians have suggested that they did so because of the limited availability of resources in their Scandinavian homelands.
For instance, arable land was more scarce in these areas. However, there is a clear consensus that not all Norse people of the time were pirates.
According to Jan Bill, a curator at the Viking Ship Museum in the Norwegian capital Oslo, even in the Viking Age, “Scandinavians never spoke of themselves as Vikings.” 
Rather, the term referred to the specific activity a Viking did. In other words, Vikings were defined by what they did rather than who they were.
Or, as Cat Jarman, an archeologist at Oslo’s Museum of Cultural History, puts it: “These identities aren’t genetic or ethnic; they’re social.” 
So, while parents can pass on Scandinavian genetic material to their children, a Viking could only become a Viking by taking to pirate, not based on birth.
Not All Vikings Were Scandinavian To Begin With
Many Vikings originated from Sweden, Denmark, and Norway. They were also distinctly marked by Norse culture.
The Viking’s pagan religion and social structures were Norse, as was the technological know-how key to their prowess—especially the swift, low-hulled longboats.
However, the Vikings soon established relations with many other people in the places they visited.
They had relationships with many of their Baltic neighbors and settled in areas of England and France.
Over time, many other people joined the Vikings in their expeditions and became Vikings themselves.
Another interesting outcome of defining Vikings by their job—as opposed to their ethnicity—is that it highlights how not all Vikings were Scandinavian, even during the Viking Age.
For instance, recent DNA studies have shown that some Vikings had Asian and Southern European ancestry. 
Others had black hair or might have been Irish.  
So, while Danes, Norwegians, and Swedes all acknowledge a Viking past, so can many other people.
Human Migrations and Population Exchange Over a Millennia
By the end of the Viking Age, in the 11th century, the descendants of Vikings were already spread far and wide across Asia and Europe.
Moreover, these populations weren’t ethnically or genetically identical, to begin with.
However, human migrations and the exchange of genetic material between various populations over the next thousand years have only made it only harder to isolate ethnically distinct populations in all but the most remote communities today.
Many Scandinavians have migrated to other parts of the world. At the same time, different groups of people have moved to Scandinavian countries.
People have intermarried between communities making establishing strict genetic boundaries harder.
It is correct to say that the Scandinavian countries are among the most homogenous of large human populations today. 
However, most studies are based on self-reported surveys that reinforce the socially constructed nature of ethnicity.
Ultimately, it isn’t easy to delineate who is Scandinavian with precision. For instance, how much Scandinavian ancestry does someone need to be considered Scandinavian?
The Vikings Didn’t Leave Written Records
A final factor that makes it hard to trace ancestry with precision is that the Vikings did not leave written records. They were a primarily oral culture. What little we know about them is from the accounts of their opponents.
The only extant texts of Norse culture are their epic poems, which are mythological and were only put down many centuries after the Viking Age ended.
The lack of written records going back centuries means that the only way to answer this question accurately would be to DNA test every single Scandinavian person.
Of course, a non-controversial assessment of who might be considered Scandinavian would be required for this. Easier said than done.
Is There No Way of Detecting Viking Ancestry?
Since neither all Vikings Norse nor all Norse were Vikings, it is impossible to detect significant Viking ancestry today.
Moreover, the Vikings did not leave written records through which elaborate family trees might be traced.
The best that can be done is to determine if a line of ancestry passed through Scandinavia sometime between the 8th and the 11th century. 
But even this does not firmly establish Viking ancestry. Diluted over millennia, remote Viking ancestors may leave only minute traces of genetic material in modern human DNA.
Seen in this light, lineage becomes a matter of percentages. Ultimately, all humans come out of Africa.