The avocado variety most widely grown worldwide is Hass.
Hass is technically a cultivar of Persea americana, not a separate avocado species. It became dominant because its creamy flesh, rich flavor, relatively thick skin, high yields, and good shipping life make it especially useful for commercial farming. The skin turns dark purplish-black as the fruit ripens, helping shoppers judge its maturity, although color alone is not a perfect test.
The cultivar originated in California from a seed planted by mail carrier and amateur horticulturist Rudolph Hass in 1926. The original mother tree produced fruit that proved more commercially valuable than the varieties Hass had intended to grow. Every commercial Hass tree descends through grafting from that original tree, whose genetic identity was later found to combine Mexican and Guatemalan avocado backgrounds.
Hass is sometimes confused with Fuerte, an older green-skinned commercial variety. Fuerte was once highly important, but Hass gradually displaced it in many markets. In the United States, Hass accounts for more than 80% of the avocado crop, and it represents roughly 80% of cultivated avocados worldwide.