Visitors to Times Square in Midtown Manhattan will have to leave pistols, revolvers and rifles at home.
New York City Mayor Eric Adams on Wednesday unveiled the first sign making the famous plaza a gun-free zone.
A new New York state law bans firearms in "sensitive places" like schools, churches and theaters from Thursday.
Empire State lawmakers issued the rule in response to a decision by the mostly conservative US Supreme Court, which eased restrictions on carrying concealed weapons in New York in late June.
At the time, however, the Supreme Court allowed states and cities to regulate firearms in “sensitive areas”.
“The Supreme Court decision tramples on the safety of all New Yorkers.
The city will defend itself against this, including through restrictions on concealed weapons in sensitive areas like Times Square," Democrat Adams said Wednesday.
The size of the square, which is one of the most visited places in the world with more than 350,000 pedestrians a day, is unclear.
Times Square used to stretch from 42nd to 47th Street.
However, the city council plans to declare the area from 40th to 53rd Streets a "gun-free zone".