Long‐term contrast‐enhanced angiography offers significant advantages in theranostics for diverse vascular diseases, particularly in terms of real‐time dynamic monitoring during acute vascular events; However, achieving vascular imaging with a duration of hours through a single administration of low‐dose contrast agent remains challenging. Herein, a hyaluronic acid‐templated gadolinium oxide (HA@Gd₂O₃) nanoprobe‐enhanced magnetic resonance angiography (MRA) is proposed to address this bottleneck issue for the first time. The HA@Gd₂O₃ nanoprobe synthesized from a facile one‐pot biomineralization method owns ultrasmall size, good biocompatibility, optimal circulation half‐life (≈149 min), and a relatively high T₁ relaxivity (r₁) under both clinical 3 T (8.215 mM⁻¹s⁻¹) and preclinical 9.4 T (4.023 mM⁻¹s⁻¹) equipment. The HA@Gd₂O₃ nanoprobe‐enhanced MRA highlights major vessels readily with significantly improved contrast, extended imaging duration for at least 2 h, and ultrahigh resolution of 0.15 mm under 9.4 T, while only requiring half clinical dosage of Gd. This technique can enable rapid diagnosis and real‐time dynamic monitoring of vascular changes in a model of acute superior mesenteric vein thrombosis with only a single injection of nanoprobe. The HA@Gd₂O₃ nanoprobe‐enhanced MRA provides a sophisticated approach for long‐term (hour scale) vascular imaging with ultrahigh resolution and high contrast through single administration of low‐dose contrast agent.