Paclitaxel is a mitotic inhibitor used in cancer chemotherapy. It was discovered in a National Cancer Institute program at the Research Triangle Institute in 1967 when Monroe E. Wall and Mansukh C. Wani isolated it from the bark of the Pacific yew tree, Taxus brevifolia and named it 'taxol'. Paclitaxel is now used to treat patients with lung, ovarian, breast cancer, head and neck cancer, and advanced forms of Kaposi's sarcoma. Paclitaxel is also used for the prevention of restenosis.

Paclitaxel works by interfering with normal microtubule growth during cell division. Together with docetaxel, it forms the drug category of the taxanes. It was the subject of a notable total synthesis by Robert A. Holton.

As well as offering substantial improvement in patient care, paclitaxel has been a relatively controversial drug. There was originally concern because of the environmental impact of its original sourcing, no longer used, from the Pacific yew.