Ifosfamide, sold under the brand name Ifex among others, is a chemotherapy medication used to treat a number of types of cancer. This includes testicular cancer, soft tissue sarcoma, osteosarcoma, bladder cancer, small cell lung cancer, cervical cancer, and ovarian cancer. It is administered by injection into a vein.

Common side effects include hair loss, vomiting, blood in the urine, infections, and kidney problems. Other severe side effects include bone marrow suppression and decreased level of consciousness. Use during pregnancy will likely result in harm to the baby. Ifosfamide is in the alkylating agent and nitrogen mustard family of medications. It works by disrupting the duplication of DNA and the creation of RNA.

Ifosfamide was approved for medical use in the United States in 1987. It is on the World Health Organization's List of Essential Medicines.

It is given as a treatment for a variety of cancers, including:

It is a white powder which, when prepared for use in chemotherapy, becomes a clear, colorless fluid. The delivery is intravenous.

Ifosfamide is often used in conjunction with mesna to avoid internal bleeding in the patient, in particular hemorrhagic cystitis.

Ifosfamide is given quickly, and in some cases can be given as quickly as an hour.

Ifosfamide is a DNA-damaging alkylating agent, belonging to the same class of chemotherapy drugs as cyclophosphamide. It is a prodrug, meaning that It has to be converted by CYP450 into its main active metabolites-(Iso)phosphoramide mustards. These metabolites form DNA cross links mainly at Guanine N-7 positions.