Abstract This study examines the financial and sustainability implications of the United States–Iran conflict on the Nigerian oil industry, focusing on the period from February 2026 to the present. The conflict, triggered by joint U.S.–Israeli military strikes on Iran and Iran's subsequent restriction of navigation through the Strait of Hormuz, has fundamentally disrupted global energy markets, driving Brent crude prices above $100 per barrel and creating both unprecedented revenue opportunities and profound structural challenges for Nigeria, Africa's largest oil producer. Drawing on a qualitative case study methodology, this research analyses secondary data from industry reports, government statements, regulatory publications, and news sources to assess the dual impact of the crisis: the fiscal windfall arising from elevated crude prices and the inflationary pressures that have eroded household purchasing power and complicated Nigeria's reform trajectory. The study finds that while Nigeria earned an estimated N5.13 trillion in oil windfall across March and April 2026, the benefits proved transient and largely price-driven rather than production-driven, with underproduction of 35.3 million barrels during the peak price period representing lost revenue that cannot be recovered. The conflict has simultaneously accelerated the strategic repositioning of the Dangote Refinery as a regional export hub while exposing the persistent vulnerability of Nigeria's oil sector to external shocks. The study concludes that sustainable benefit from such geopolitical disruptions requires deliberate conversion of windfall gains into structural investment rather than short-term fiscal spending, and recommends the establishment of a stabilization fund, accelerated upstream production recovery, and diversified export market development. Keywords: US-Iran conflict, Nigerian oil industry, fiscal sustainability, oil windfall, energy security