Rapeseed oil is one of the oldest known vegetable oils. There are both edible and industrial forms produced from rapeseed, the seed of several cultivars of the plant family Brassicaceae (mustards). The term "rapeseed" applies to oilseeds from the species Brassica napus and Brassica rapa, while the term canola refers to specific rapeseed varieties bred to produce oil for use in human and animal foods. In manufacturing, the edible varieties of canola are required to contain less than 2% erucic acid in Canada, the United States, European Union, and many other countries.

Canola is produced as low erucic acid rapeseed (LEAR) oil and is generally recognized as safe (GRAS) by the United States Food and Drug Administration (FDA).

In commerce, non-food varieties are typically called colza oil. In 2022, Canada, Germany, China, and India were the leading producers of rapeseed oil, accounting together for 41% of the world total.

The name for rapeseed comes from the Latin word rapum meaning turnip. Turnip, rutabaga (swede), cabbage, Brussels sprouts, and mustard are related to rapeseed. Rapeseed belongs to the genus Brassica. Brassica oilseed varieties are some of the oldest plants cultivated, with documentation of its use tracing back to India from 4,000 years ago, and use in China and Japan 2,000 years ago. Its use in Northern Europe for oil lamps is documented to have started in the 13th century. Rapeseed oil extracts were first put on the market in 1956–1957 as food products, but these had several unacceptable properties. That form of rapeseed oil had a distinctive taste and a greenish colour due to the presence of chlorophyll, and still contained a higher concentration of erucic acid.

Canola was bred from rapeseed cultivars of B. napus and B. rapa at the University of Manitoba in the early 1970s. Its nutritional profile was then different from present-day oil, as well as containing much less^[more?] erucic acid. This work was performed at the National Research Council of Canada laboratories in Saskatoon using gas liquid chromatography. Canola was originally a trademark name of the Rapeseed Association of Canada; the name is a portmanteau of "can" from Canada and "ola" from "oil". Canola is now a generic term for edible varieties of rapeseed oil in North America and Australasia; the change in name also serves to distinguish it from natural rapeseed oil, which has much higher erucic acid content.

A genetically engineered rapeseed that is tolerant to the herbicide Roundup (glyphosate) was first introduced to Canada in 1995 (Roundup Ready). A genetically modified variety developed in 1998 is considered to be the most disease- and drought-resistant canola variety to date. In 2009, 90% of the Canadian crop was herbicide-tolerant. In 2005, 87% of the canola grown in the US was genetically modified. In 2011, out of the 31 million hectares of canola grown worldwide, 8.2 million (26%) were genetically modified.

A 2010 study conducted in North Dakota found glyphosate- or glufosinate-resistance transgenes in 80% of wild natural rapeseed plants, and a few plants that were resistant to both herbicides. This may reduce the effectiveness of the herbicide tolerance trait for weed control over time, as the weed species could also become tolerant to the herbicide. However, one of the researchers agrees that "feral populations could have become established after trucks carrying cultivated GM seeds spilled some of their load during transportation". She also notes that the GM canola results they found may have been biased as they only sampled along roadsides.

Genetically modified canola attracts a price penalty compared to non-GM canola; in Western Australia, it is estimated to be 7.2% on average.