Everything from a UTI, sexually transmitted infection (STI), bacterial or viral infection in your urethra (urethritis), interstitial cystitis (inflamed bladder wall), vaginal yeast infection, bacterial vaginosis (a condition that disrupts the normal balance of bacteria in the vagina), atrophic vaginitis (thinning, drying, and inflammation of vagina walls owing to a lack of estrogen), and vulvodynia (chronic pain in your private parts) can cause a burning sensation while peeing after sex. 

Injuries related to childbirth and cervical issues can also be to blame when it comes to women, whereas for men, it could mean prostatitis (inflammation of the prostate gland) or a yeast infection (via Medical News Today). 

When it comes to these causes, it’s important to keep an eye out for other symptoms too. For example, with a UTI, you may experience pelvic pain and cloudy and foul-smelling urine, and with urethritis, there could be a frequent urge to pee and itching in your private parts. A burning sensation while peeing sometimes might be the only symptom of an STI like chlamydia, herpes, or trichomoniasis (via Healthline), but other signs include blisters, itching, and swelling in the affected area. Prostatitis could present with fevers and chills and bloody or cloudy urine and yeast infections can include symptoms like gray discharge, swelling in your private parts, and a rash.