Adgillis II was an obscure historical figure who may have been Ruler of Frisia

Frisia

Frisia is a coastal region along the southeastern corner of the North Sea, i.e. the German Bight. Frisia is the traditional homeland of the Frisians, a Germanic people who speak Frisian, a language group closely related to the English language...

 between 734 and 741. No contemporary accounts of his rule exist, but the scanty information available suggests that King Poppo

Poppo (Frisian)

Poppo , also known as Bubo or Bobba, was a king of Frisia from the 8th century. After Aldgisl and Radboud he is the third Frisian ruler mentioned in the literature. He is possibly the last Frisian king...

 (ruled 719-734) was succeeded by someone called Adgillis. Eggerik Benninga made a brief record in his 16th century chronicle of the Frisians. This information would have been based on earlier documents that have since been lost.

Adgillis II may have been the third son of King Radboud

Radbod, King of the Frisians

Radbod was the king of Frisia from c. 680 until his death. He is often considered the last independent ruler of Frisia before Frankish domination. He defeated Charles Martel at Cologne. Eventually, however, Charles prevailed and compelled the Frisians to submit...

, Poppo's predecessor. Adgillis II was probably Poppo's brother. Poppo himself died in the Battle of the Boarn

Battle of the Boarn

The Battle of the Boarn was an eighth century battle between the Franks and the Frisians near the mouth of the river Boarn in what is now the Dutch province of Friesland....

 against the Franks

Franks

The Franks were a confederation of Germanic tribes first attested in the third century AD as living north and east of the Lower Rhine River. From the third to fifth centuries some Franks raided Roman territory while other Franks joined the Roman troops in Gaul. Only the Salian Franks formed a...

 in 734. This Frisian defeat allowed Charles Martel

Charles Martel

Charles Martel , also known as Charles the Hammer, was a Frankish military and political leader, who served as Mayor of the Palace under the Merovingian kings and ruled de facto during an interregnum at the end of his life, using the title Duke and Prince of the Franks. In 739 he was offered the...

 to capture all of the Kingdom of Frisia west of Lauwers

Lauwers

The Lauwers is a river in the Netherlands. It forms part of the border between the provinces of Friesland and Groningen. From the 730's to Widukind's defeat in 785 it was part of the border of the Frankish Empire....

. The Frisian controlled lands were limited to the coast and islands. It is at this point that Adgillis II would have succeeded Poppo.