His son, Majd Haidar, the owner of Ward publishing house, announced his passing on his Facebook page, saying, "The Leopard left us to his kingdom," referring to the protagonist of his 1968 novel The Leopard, which was adapted into a film with the same name by the late Syrian director Nabil Al-Maleh.

Haidar was born in the village of Hussein Al-Baher on the Syrian coast in 1936. He began his career as a teacher of Arabic in Algeria before settling in Beirut where he worked in publishing. During the Lebanese civil war, he joined the Palestinian resistance movement and later worked as a culture editor of Al-Mawqef Al-Arabi and Sawt Al-Bilad in Cyprus.

Haidar was known for his critical stance towards political and religious institutions and his willingness to tackle controversial topics in his writing. He wrote seventeen books of fiction, short fiction, essay and biography, including The Desolate Time, which was chosen by the Arab Writers Union as one of the best 105 books of the 20th century.

Although none of his book-length works have been translated into English, an excerpt from his novel A Banquet for Seaweed and his short story The Silence of Fire have been translated and published in English-language literary journals.

Haidar's works were often the subject of controversy and censorship, particularly A Banquet for Seaweed, which was banned in several Arab countries. The novel sparked protests in Cairo in 2000 when it was reprinted, leading to its confiscation and accusations of heresy and offending Islam leveled against Haidar by Al-Azhar University clerics.

Despite these challenges, Haidar remained committed to his critical perspective and his oppositional stance. As Hisham Bustani writes in the introduction to his interview with Haidar in The Common in 2019: "Despite changing times, Haidar has not been defeated by censorship—either imposed by others or himself.”

“He has kept a fierce, critical distance from all sides: the dictatorship of the ruling regime in his country of Syria; the dictatorship of public taste and ‘conventions;’ the oppression of dogmatic ideology and the ruling party; the tyranny of power derived from religion.”

Haidar Haidar saw culture as the last wall of resistance in the Arab world, without which the Arab nation would collapse. He stated in several interviews that "in light of the political decline that the Arab world is experiencing, all gates to the future and hope have been closed, and only the enlightened and deep culture remains, which is responsible for shedding light at the end of the tunnel and illuminating this darkness."