Sayyiduna Ali (may Allah be pleased with him) said: Any woman who marries without the permission of her guardian, her marriage is void; there is no marriage except with the permission of a guardian.
This chain is sahih (authentic). It has also been narrated from Ali (may Allah be pleased with him) through other chains, though reliance is on this one rather than those.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 13641