Yes, alcohol can dehydrate you. Alcohol is a diuretic. It causes your body to remove fluids from your blood through your renal system, which includes the kidneys, ureters, and bladder, at a much quicker rate than other liquids. If you don't drink enough water with alcohol, you can become dehydrated quickly.
"The higher the alcohol content a drink has (or is absorbed in your body), the greater the diuretic and dehydration effect." Drinks with a higher alcohol content — and therefore more potential to dry you out — include vodka, gin, rum, and whisky.
Alcohol does the opposite. It reduces how much ADH you make, so it increases how much urine you produce. Each shot of alcohol that you drink forces your kidneys to generate an extra 120 millilitres of urine on top of the normal 60–80 millilitres per hour.