Isaac A. Van Amburgh (1808–1865) was an American animal trainer who developed the first trained wild animal act in modern times. By introducing jungle acts into the circus, Van Amburgh paved the way for combining menageries with circuses. After that, menageries began using equestrian and clown performances in circus rings. Gradually the distinction between circus and menagerie faded.

From the humble beginning of cage-cleaner in the Zoological Institute of New York, Van Amburgh quickly gained notoriety for his acts of daring, for example placing his bare arm and even head inside the jaws of a wild cat. Also known for his domineering attitude toward his animals, he earned the title "The Lion King."

Despite the disapproval of some for his brutal treatment of animals, Van Amburgh remained very popular and successful, beginning his own menagerie which he took to Europe. He died a wealthy man, and his name continued to be used in the circus world for more than a century after.

Isaac A. Van Amburgh (a name adopted by his American Indian grandfather) was born on May 26, 1808, in Fishkill, New York. Van Amburgh's early life, though atypical, proved to be of great training for his later adventures as "the Lion King." Van Amburgh's father died when he was still an infant, leaving him and his mother with very little. The night before Amburgh was born, his mother had a strange dream. According to Richard Horne in The Life of Van Amburgh, the Brute-Tamer: With Anecdotes of His Extraordinary Pupils, she dreamt that she walked into an old barn with rows of cooking kettles lined up. As she opened the kettles one by one, she found different parts of a lion's body cooking in the kettle. She then proceeded to devour the lion part by part and put the lion's whole head in her mouth. She woke up extremely disturbed, having no idea what this dream meant for her son's future. Horne goes on to describe how Isaac's mother was constantly worried about him while he was growing up. Legend dictates that while reading the Bible, young Isaac came upon the tale of Daniel in the lion's den, and, from then on, was determined to be a lion tamer. Van Amburgh never showed the same interests in material objects or even games as the other children. Rather, he spent his time surrounded by roaches, mice, and rats, feeding them pieces of his dinner to attract and even train them. He soon became a sort of animal authority to call when the local wildlife disrupted neighborhood homes and farms. Van Amburgh would investigate reports of destroyed or stolen crops and livestock and seek out the animal responsible. Upon finding the offender, he would beat the creature into submission, effectively preventing it from causing additional problems. He found his start in the Zoological Institute of New York.

At nineteen, Isaac left his home in Peekskill, New York to look for a job in neighboring North Salem. There he found a job as a cage cleaner in the Zoological Institute of New York.

Despite its lofty-sounding name, the Zoological Institute was not a zoo at all, but rather a tiny traveling menagerie. In a period of time when amusement was regarded with suspicion, it was from its name that this show got its value.

Although he started out as a "cage boy," Isaac showed an aptitude for training the wild animals whose cages he cleaned. One of the owners of the Zoological Institute, Titus, was a dealer in wild animals. So he appreciated the novelty of trained wild animals, recognizing that "novelty plus publicity meant money."

June, Titus, and Angevine distributed posters by the thousands. They put Isaac in costume – a Roman toga, in reference to the gladiators of ancient Rome's Circus Maximus. In the winter, Van Amburgh trained his wild animals in the barns of New York's upper Westchester and the lower Putnam counties. The next year, 1821, the Van Amburgh Menagerie hit New York City.