Sarel Arnoldus Cilliers was a Voortrekker leader and a preacher. With Andries Pretorius, he led the Boers to a huge victory over the Zulus at the Battle of Blood River in 1838. In particular, Cilliers lead the Voortrekkers in a vow which promised that if God would protect them and deliver the enemy into their hands, they would build a church and that the day of their victory would be commemorated as if it was a Sunday by them and their descendants.

He was a prominent member of the Gereformeerde Kerk (Reformed Church),

The town of Kroonstad was, according to folklore, named after a horse belonging to Cilliers, which drowned in a stream (Kroonspruit) where the town is situated.

There is a Sarel Cilliers Museum as well as a statue of him (on the site of the Dutch Reformed Church) in Kroonstad. Numerous streets and roads in Kroonstad and throughout South Africa are named after him.