Poienari Castle is a ruined castle in Romania, in Arges County on a canyon formed on the Arges River valley, close to the Fagaras Mountains. It stands on a cliff, on the right side of the Transfagarasan road which climbs high into the mountains.

It was erected around the beginning of the 13th century by the first Romanian ruler in the South region of Romania, known as Wallachia. Around the 14th century, Poienari was the main citadel of the Basarab rulers. In the next few decades, the name and the residents changed a few times but eventually the castle was abandoned and left in ruins.

However, in the 15th century, realizing the potential for a castle perched high on a steep precipice of rock, Vlad Tepes repaired and consolidated the structure, making it one of his main fortresses. Vlad Tepes is known better to the Western world as Vlad the Impaler, or Dracula and that's why the castle attracts a number of tourists, due to its strong connection with him. Bram Stoker's book says that Romanians know it as "Cetatea Lui Negru Voda" or Citadel of the Black Ruler, although the castle in the book was situated some 200 km to the North.

Although the castle was used for many years after Vlad's death in 1510, it eventually was abandoned again in the first half of the 16th century and was in ruins during the 17th century. Due to its size and location, the castle was very hard to seize, even by natural forces. However, in 1888, a landslide brought down a portion of the castle which crashed into the river far below. Nonetheless, the castle was slightly repaired and the walls and its towers still stand today.