Lady Gaga, Kerry Washington and Debra Messing urged voters to #StayInLine amid reports of hours-long queues during the final hours of polling for the US midterm elections.
New York, Georgia, Arizona and Texas are among the states said to have had lengthy waiting times for voters while malfunctioning equipment caused problems elsewhere.
The hashtag #StayInLine was trending Twitter on Tuesday evening as voting went down to the wire.
A Star is Born actress Gaga was among the celebrities encouraging voters not to give up.
She tweeted: “If you’re in line, stay in line. Every vote counts! #StayInLine.”
Will & Grace star Messing told voters in Georgia pizza and drinks were on the way for those still queuing up.
She added: “STAY IN LINE! We support you and thank you!”
Scandal actress Washington wrote: “Tweeple!!! There is still time to vote! If you are in line, PLEASE STAY IN LINE. As long as you are in line at your site before the polls close you have the right to vote. #ElectionDay #WeMatter.”
The rapper Common shared helpline numbers for anyone having issues voting and said: “#StayInLine. We got this fam!”
And former presidential nominee Hillary Clinton said: “For voters in Georgia and elsewhere who are waiting in long lines to vote: You have the right to vote as long as you’re in line when the polls close.
“Please stay in line, encourage those around you to do the same, and help bring this home for @StaceyAbrams. #StayInLine.”
According to official figures, 36 million people voted early for the midterms, with some pundits claiming this indicated a large turnout on polling day.