Poppo I (also Boppo; died 13 July, before 1044) was Margrave of Istria from 1012 and of Carniola from 1040 to his death.
Poppo was the son of a comital family from Weimar in the Imperial Landgraviate of Thuringia. His father was either Count William II or William III of Weimar, his mother probably Oda, daughter of the Saxon margrave Thietmar.
He married Hadamut, the daughter of Count Weriand, who had received large estates in Friuli and Istria, then part of the Carinthian duchy, from the hands of Emperor Otto III. Poppo thus inherited a claim to the Istrian peninsula and began to use the margravial title. After King Henry III of Germany had inherited Carinthia, he in 1040 established the Marches of Istria and Carniola. As his wife's mother was related to the Bavarian Counts of Ebersberg, who held possessions in Carniola, Poppo was also appointed Carniolan margrave.
Hadamut gave him one son, Ulric I, who succeeded his father in 1045.
| Preceded by new creation |
Margrave of Istria 1012–1044 |
Succeeded by Ulric I |
| Preceded by new creation |
Margrave of Carniola 1040–1044 |
Succeeded by Ulric I |