Ingvaeonic /ˌɪŋviːˈɒnɪk/, also known as North Sea Germanic, is a postulated grouping of the West Germanic languages that comprises Old Frisian, Old English and Old Saxon.

Ingvaeonic is named after the Ingaevones, a West Germanic cultural group or proto-tribe along the North Sea coast. It is not thought of as a monolithic proto-language, but rather as a group of closely related dialects that underwent several areal changes in relative unison.

The grouping was first proposed in Nordgermanen und Alemanen (1942) by German linguist and philologist Friedrich Maurer (1898–1984), as an alternative to the strict tree diagrams which had become popular following the work of 19th century linguist August Schleicher and which assumed the existence of a special Anglo-Frisian group. The other groupings are Istvaeonic, from the Istvaeones, including Netherlandic, Afrikaans, and related languages; and Irminonic, from the Irminones, including the High German languages.

Linguistic evidence for Ingvaeonic are common innovations observed in Old Frisian, Old English and Old Saxon such as the following: