Mustard seed oil is a vegetable oil extracted from the seeds of several types of mustard: white Sinapis alba, brown Brassica juncea, yellow Brassica hirta, and black Brassica nigra. The seeds contain 30-40% oil by weight, extracted by mechanical pressing or by solvent extraction. The oil is distinguished by a unique sharp, pungent flavor resulting from the compound allyl isothiocyanate.

Mustard cultivation has a history extending more than five thousand years in the Fertile Crescent and the Nile basin, and it is one of the oldest spices in the world. Its traditional use became renowned in India, Pakistan, and Bangladesh, where the oil is considered the main cooking oil. Canada, the European Union, India, Nepal, and Russia lead global seed production.

Traditional mustard oil has a unique composition containing a high proportion of erucic acid (C22:1) ranging from 30-50%, along with oleic acid (20-30%), linolenic acid (omega-3, 10%), and linoleic acid (omega-6, 15%). The omega-6:omega-3 ratio is about 4:1, excellent for health. However, erucic acid at high levels is considered harmful to health, so low-erucic varieties similar to canola oil were developed. Importing traditional oil for human consumption is banned in the United States and the European Union.

Detailed USDA-FAS data are not available for mustard oil production, as it is a specialty oil. India is the main market for the oil as food, and the local product is made in large but internationally unrecorded quantities. Canada and the European Union produce the low-erucic varieties for Western markets. The oil is governed by Codex Alimentarius standard CXS 210-1999.

Mustard oil is widely used in food in Indian, Bangladeshi, and Pakistani cuisine (for frying, pickles, and curry), and in Bengal it is heated before use to soften its pungent flavor. Industrially, it goes into the making of pickles, mustard sauce, and condiments. The high-erucic varieties are used in making industrial lubricants, bioplastics, and biofuel.