language and literary scholar whose works stimulated interest in the study of Anglo-Saxon (Old English) and the cognate old Germanic languages.

Son of Franciscus Junius, a French Protestant theologian, he was educated in theology and became a pastor in the Netherlands (1617), but in 1620 he went to England as librarian and family tutor to the noted patron of the arts Thomas Howard, 14th Earl of Arundel. Remaining in England for 30 years, he gathered a rich collection of ancient manuscripts, which he edited and annotated and bequeathed to the Bodleian Library, Oxford. During the first two years of his return to the Netherlands (1651–74), he lived in Friesland, the northern part, in order to study the old dialect. In 1674 he returned to England and, in 1676, retired to Oxford.

He prepared an edition (1655) of the Caedmon poems, a fragment of verse attributed to Caedmon, the earliest English Christian poet. Probably his most important work was the preparation of the first edition (1665) of the Gothic codex of the 4th-century bishop Ulfilas. His Etymologicum Anglicanum (1743; “English Etymology”) was used extensively by Samuel Johnson.