Remove as much as possible with a snake or drain cleaning tool. Pour ½ cup baking soda then ½ cup white vinegar in the drain and cover, letting sit for 20 minutes. Boil water, remove cover, and pour water down the drain. You may have to repeat the process.
We unclog our bathroom drains with a long snake-like piece with barbed edges that grab the hair. https://amzn.to/2LQ1Y7m
Just to confirm, I agree with Kathy. We keep ours running good by occasionally putting baking soda then vinegar down drains followed with a hot water rinse. Wishing you the best.
We use a small "snake" that you can find at your hardware store...we got ours at Home Depot.
If you have one of those permanent drain plugs, you may have to unscrew it and take it out to get a good cleaning.
If this has been a problem for a long time, it may take some effort to get it cleaned out...such as taking out the "P Trap" and clearing it.