100 thousand million stars

Stars are not scattered randomly through space, they are gathered together into vast groups known as galaxies. The Sun belongs to a galaxy called the Milky Way. Astronomers estimate there are about 100 thousand million stars in the Milky Way alone. Outside that, there are millions upon millions of other galaxies also!

http://m.esa.int/Our_Activities/Space_Science/Herschel/How_many_stars_are_there_in_the_Universe

It has been said that counting the stars in the Universe is like trying to count the number of sand grains on a beach on Earth.