Ciprofloxacin is a fluoroquinolone antibiotic used to treat a number of bacterial infections. This includes bone and joint infections, intra-abdominal infections, certain types of infectious diarrhea, respiratory tract infections, skin infections, typhoid fever, and urinary tract infections, among others. For some infections it is used in addition to other antibiotics. It can be taken by mouth, as eye drops, as ear drops, or intravenously.

Common side effects include nausea, vomiting, and diarrhea. Severe side effects include an increased risk of tendon rupture, hallucinations, and nerve damage. In people with myasthenia gravis, there is worsening muscle weakness. Rates of side effects appear to be higher than some groups of antibiotics such as cephalosporins but lower than others such as clindamycin. Studies in other animals raise concerns regarding use in pregnancy. No problems were identified, however, in the children of a small number of women who took the medication. It appears to be safe during breastfeeding. It is a second-generation fluoroquinolone with a broad spectrum of activity that usually results in the death of the bacteria.

Ciprofloxacin was patented in 1980 and introduced in 1987. It is on the World Health Organization's List of Essential Medicines. The World Health Organization classifies ciprofloxacin as critically important for human medicine. It is available as a generic medication. In 2020, it was the 132nd-most-commonly prescribed medication in the United States, with more than 4 million prescriptions.