Sector 3 is an administrative unit of Bucharest. It is the most populous, most densely populated and also the third-largest division of the city. Actually, at its total population of over 460 thousand, it is the second-most populated administrative area of Romania, only after the capital city. It is also the most important of all six sectors of Bucharest, as it includes the Downtown Bucharest, the Kilometre Zero and other significant landmarks. It is bordered by Sector 2 to the North, Ilfov County to the East, Sector 4 to the South, Sector 5 to the Southwest and Sector 1 to the Northwest.
The largest and most populous district of Sector 3 is Titan. Lipscani, colloquially known as oldtown is the center of the nightlife in Bucharest, and also the biggest attraction for foreign tourists. Also notable, the Bucharest Mall is located inside the Vitan district of the Sector 3. Two of the sector's districts have been described as the most pleasant by Bucharest citizens.