Oleanolic acid is a naturally occurring triterpenoid related to betulinic acid. It is widely distributed in food and plants. Oleanolic acid can be found in olive oil, Phytolacca americana (American pokeweed), and Syzygium spp, garlic, etc. It was first studied and isolated from several plants, including Olea europaea (leaves, fruit), Rosa woodsii (leaves), Prosopis glandulosa (leaves and twigs), Phordendron juniperinum (whole plant), Syzygium claviflorum (leaves), Hyptis capitata (whole plant), Mirabilis jalapa and Ternstromia gymnanthera (aerial part). Other Syzygium species including java apple (Syzygium samarangense) and rose apples contain it.

Oleanolic acid is relatively non-toxic, hepatoprotective, and exhibits antitumor and antiviral properties. Oleanolic acid was found to exhibit weak anti-HIV and weak anti-HCV activities in vitro, but more potent synthetic analogs are being investigated as potential drugs.