A bladder infection, also known as cystitis, is a common type of urinary tract infection (UTI) that occurs when bacteria enter and multiply within the bladder. It is more frequent in women due to anatomical differences but can affect individuals of any age or sex. Typical symptoms include a strong, persistent urge to urinate, burning during urination, cloudy or strong-smelling urine, pelvic discomfort, and frequent passage of small amounts of urine. In some cases, mild fever or blood in the urine may occur. Most bladder infections are caused by bacteria such as *Escherichia coli* and are treated effectively with antibiotics. Prompt treatment is important to prevent the infection from spreading to the kidneys, which can lead to more serious complications.