Senjak (Serbian Cyrillic: Сењак, pronounced [sêɲaːk]) is an urban neighborhood of Belgrade, the capital city of Serbia. Located in Savski Venac, one of the three municipalities that constitute the very center of the city, it is an affluent neighborhood containing embassies, diplomatic residences, and mansions. Senjak is generally considered one of the wealthiest parts of Belgrade.

Before it became interesting to Belgrade's upper classes, Senjak was an excellent natural lookout. As many farmers kept their hay throughout the entire city, fires were quite frequent, so it was ordered for hay to be collected and kept in one place, and the area of modern Senjak was chosen, apparently also getting its name in the process (from the word seno, Serbian for hay). Especially bad was the fire in the late September 1857, when almost all stacks of hay stored in the Belgrade Fortress burned. Also, the hay for army horses was kept here in the late 19th century. A more romantic theory of the neighborhood's name (from the word sena, Serbian for 'shade' or 'shadow') developed later.

On the east, Senjak was bounded by the Topčider Road, which connected downtown Belgrade to the forests of Košutnjak and Topčider. The road section on the northern slope, between Senjak and western part of Točidersko Brdo, is today named Bulevar Vojvode Putnika. This section of the street was embellished with the quadruple chestnut avenue in the late 19th century. Southern section, which swerved around Senjak, was embellished with the avenue of poplars. Senjak and the neighboring Topčidersko Brdo are today quite wooded for the urban areas. This is the result of the 1923 Belgrade's general plan. One of the main projects regarding the green areas was forestation of the hill, formation of the new park and establishment of the continuous green area with the Topčider Park. Project started in 1926 while the Hyde Park was finished in the 1930s. Today, the continuous Topčider-Košutnjak parks and forests make the largest "green massif" in the immediate vicinity of Belgrade's urban tissue.

The settlement began to form around the tobacco factory, which was built before World War I. Several hundred of houses and hovels were built around the factory, mostly by the factory workers. Soon, workers from the neighboring industrial facilities along the Topčider Road, including the State Postage Stamp Printing Office (Markarnica), railway workers, etc. The workers settlement developed mostly along the road to the old quarry. At the time, the hill was known for the greenery and abundant fruit production, mainly apricots, grapes and figs. Lower classes had various advantages living in Senjak at the time: their workplaces were close when the public transportation grid wasn't that much developed, the costs of living outside of the city were lower, they could grow their food and fruits, there was a direct tram line to downtown and the railway also passed through the settlement.

The tobacco factory was destroyed by the Austro-Hungarian bombing of Belgrade in 1914 and wasn't rebuilt after the war. This left room for numerous workers houses to be demolished, too, and they were massively being sold due to the increased prices of the land. Instead, many villas were built by the most affluent Belgrade families. Senjak became one of the neighborhoods of Belgrade with most striking difference between social classes. Top of the Senjak Hill was occupied by the most lavish private houses in the city, while the edges and areas below the hill were among the most desolate parts of Belgrade (Prokop, Jatagan Mala).

During the 1999 NATO bombing of Serbia, a number of buildings in the neighborhood such as the Swiss ambassador's residence were damaged or affected by the conflict.

The first tram link established in Belgrade was from the Kalemegdan fortress to Senjak.

Senjak is located 3 km south-west of downtown Belgrade, on top of the hilly cliff-like crest of the western slopes of Topčidersko Brdo, overlooking Belgrade Fair right below and the Sava river (from which, at the closest point, Senjak is only 100 meters away). It borders the neighborhoods of Topčider and Careva Ćuprija (south), Mostar (north), Prokop and Dedinje (east). The triangularly shaped neighborhood has many smaller streets but it is bounded by two wide boulevards, named after Serbian army vojvodas from World War I: Vojvoda Mišić and Vojvoda Putnik.