Zar'a Ya`qob or Zera Yacob ("Seed of Jacob," 1399–1468) is nəgusä nägäst (19 or 20 June 1434–1468) of Ethiopia (throne name Kwestantinos I or Constantine I), and a member of the Solomonic dynasty.

Born at Tilq in the province of Fatagar (now part of the Oromia Region, near the Awash River), Zara Yaqob is the youngest son of Dawit I and his youngest queen, Igzi Kebra.

The British expert on Ethiopia, Edward Ullendorff, stated that Zara Yaqob "was unquestionably the greatest ruler Ethiopia had seen since Ezana, during the heyday of Aksumite power, and none of his successors on the throne – excepted only the emperors Menelik II and Haile Selassie – can be compared to him."

Paul B. Henze repeats the tradition that the jealousy of his older brother Tewodros I forced the courtiers to take Zara Yaqob to Tigray where he was brought up in secret, and educated in Axum and at the monastery of Dabra Abbay.

While admitting that this tradition "is invaluable as providing a religious background for Zar'a-Ya'iqob's career", Taddesse Tamrat dismisses this story as "very improbable in its details."

The professor notes that Zara Yaqob wrote in his Mashafa Berhan that "he was brought down from the royal prison of Mount Gishan only on the eve of his accession to the throne.