In urology, a Foley catheter (named for Frederic Foley, who produced the original design in 1929) is a flexible tube that a clinician passes through the urethra and into the bladder to drain urine. It is the most common type of indwelling urinary catheter.

The tube has two separated channels, or lumina (sg. lumen), running down its length. One lumen, open at both ends, drains urine into a collection bag. The other has a valve on the outside end and connects to a balloon at the inside tip. The balloon is inflated with sterile water when it lies inside the bladder to stop it from slipping out. Manufacturers usually produce Foley catheters using silicone or coated natural latex. Coatings include polytetrafluoroethylene, hydrogel, or a silicon elastomer – the different properties of these surface coatings determine whether the catheter is suitable for 28-day or 3-month indwelling duration.

Foley catheters should be used only when indicated, as use increases the risk of catheter-associated urinary tract infection (UTI) and other adverse effects. While female sex is generally recognised as a risk factor for UTIs, the differences in biological sex are reduced or even diminished while carrying catheters.