Rabih az-Zubayr ibn Fadl Allah (Arabic: رابح فضل الله ,رابح الزبير ابن فضل الله; c. 1842 – April 22, 1900), also known as Rabih Fadlallah and usually known as Rabah in French, was a Sudanese warlord and slave trader who established a powerful empire east of Lake Chad, in today's Chad.

Born around 1842 to an Arabic tribe in Halfaya Al-Muluk, a suburb of Khartoum, he first served with the irregular Egyptian cavalry in the Egyptian–Ethiopian War, during which he was wounded.

In the 19th century, Khartoum had become a very important Arab slave market, supplied through companies of Khartumi established in the region of Bahr el Ghazal, where they resided in zaribas (Arabic: زريْـبـة, romanized: zarība), thornbush-fortified bases kept by bāzinqirs (firearm-equipped slave soldiers,[1] borrowed from Ottoman Turkish: basgıncı er, lit. 'raider').

Using the tactics of the Khartumi, in the 1880s he carved out a kingdom between the basins of the Nile and the Ubangi, in the country of Kreich and Dar Benda, south of Ouaddai, a region he utterly devastated.

In 1887, Rabih's forces invaded Darfur, recruited bazingirs, and settled down in Dar Kouti; however, his campaign against the aguid Salamat Cherif ed-Din, commander of the sultan of Ouaddai's troops, failed.

In 1890, he attacked the Muslim chief Kobur in the north of Oubangui-Chari, deposed him and established in his place his nephew Mahdi al-Senoussi, on whom he imposed his suzerainty.

In the south-east of Lake Chad, he attacked the Baguirmi Kingdom in 1892, blaming the Mbang (king) Abd ar Rahman Gwaranga for having signed a protectorate with the French.

On the road to Borno, Rabih made prisoner the sultan of Karnak Logone, whose capital promptly opened its doors to his host.

Shehu Ashimi of Borno sent 15,000 men to confront Rabih; the latter routed them in May or September 1893 first at Am Hobbio (south of Dekoa) and then at Legaroua with only 2,000 horses.

Wanting to modernize his army, Rabih attempted in 1895 to make an accord with Royal Niger Company in Yola and Ibi so to obtain gunpowder and ammunition, but without success.

He promulgated a legal code based on sharia, rationalized taxation through the creation of a budget, imposed on Borno a military dictatorship, which aroused the attention of the colonial powers.

More importantly, Rabih launched a regular series of razzias to plunder and capture slaves; this was a return to the traditional activity of the sultans of Borno, which had been described in 1526 by Leo Africanus.

On July 17, Lieutenant Bretonnet, who had been sent by France against Rabih, was killed with most of his men at the battle of Togbao, at the edge of the Chari River, in present-day Sarh.

Rabih gained three cannons from this victory (which the French recaptured at Kousséri) and ordered his son Fadlallah, whom he had left in Dikoa, to hang Béhagle.In response, a French Army column, proceeding from Gabon and led by Émile Gentil, supported by the steamboat Leon Blot, confronted Rabih at Kouno at the end of the year.