The legendary kings of Denmark were, according to legend, the monarchs of Denmark, the Danes, or specific lands of Denmark (Zealand, Jutland or Scania) who preceded Gorm the Old, a king who reigned c. 930s to c. 960s and is the earliest reliably attested Danish ruler. Gorm's son, Harald Bluetooth, oversaw the widespread Christianization of Denmark, meaning that the legendary kings listed here are those from before Christianization and are predominantly (but not entirely) pagan. Kings preceding Gorm may be partly historical (especially those near to Gorm's time), but are either semi-legendary or entirely mythological. Some are based on earlier euhemerised stories (that is, figures from mythological folktales were depicted as historical kings by medieval writers such as Saxo Grammaticus).

There are many medieval accounts of the Danish kings of the Dark Ages, and these accounts can be confusing and contradictory (although there is overlap and different sources can include the same kings). This article presents the legendary kings from each source separately.

Runestones are raised stones, marked with a runic inscription. In the Viking Age, and especially later in the Viking Age, runestones were often raised in memorial of dead people, including kings. Many were raised by contemporaries of the deceased, making runestones important archeological and historical evidence. Although they contain very little detail about the people they mention, they are vital corroborating evidence for individuals (especially kings) that are known of through other sources (see below).

Surviving runestones that were found in lands that were part of Denmark during the Viking Age and refer to early and legendary kings of Denmark include:

In summary, the legendary Danish kings preceding Gorm the Old who are recorded on Viking Age runestones are:

Adam of Bremen was an 11th century German chronicler. Although not Danish himself, he spent time in the court of the Danish king Svend Estridson. Adam claims to derive much of the information on Danish history from his Latin chronicle Gesta Hammaburgensis ecclesiae pontificum ("Deeds of the Bishops of Hamburg") from conversations with Svend (whom he quotes verbatim in several places) and from information provided by Danish bishops. He also references the historians of the Franks (see, for example, the section on the Royal Frankish Annals, below) and hagiographies such as Vita Ansgarii.

Gesta Hammaburgensis ecclesiae pontificum names several 10th century kings preceding Gorm the Old. Kings whose histories are derived from information provided by Svend Estridson include:

Mentioned kings preceding Gorm the Old, whose histories are derived from other sources, include: