Ari Nagel (1975 or 1976[1]) is an American mathematics professor and a sperm donor[1] who has fathered more than 165 children as of June 2024[update].

[2] He has been nicknamed the Sperminator[3] or the Target Donor, after the American retail corporation in whose stores some of his artificial-insemination donations were performed.

[5] Shortly after the story was published, the New York State Department of Health sent Nagel a letter informing him that operating an unlicensed sperm bank was illegal, but did not escalate the matter.

[3] As of 2021, Nagel continued to operate outside of any regulatory framework, and provides sperm donations without formal legal contracts.

He has been successfully sued by five mothers (of nine children) for child support, and half of his university paycheck is garnished towards these payments.

[9] In 2018, Israeli authorities banned him from donating sperm; his appeal against the decision was rejected by the Supreme Court of Israel.