A woman was robbed of her cellphone in Union Square on Tuesday, police said.

The 47-year-old victim was holding her phone while walking in the 300 block of Geary Street about 4:30 p.m. when a man who appeared to be in his 30s approached her from behind and put her in a headlock, police said.

The thug then pushed her against a nearby building, took her phone and fled.

No arrest was made.