There is no definitive answer to this question as it is impossible to measure the length of someone's arms without them being present. However, there are a few contenders for the title of 'longest arms ever'.
One such contender is Jyoti Amge, who holds the Guinness World Record for being the world's smallest living woman. Amge is just 61.95 centimeters (24.3 inches) tall and her arms are only 28 centimeters (11 inches) long - making her proportions quite extreme. Another contender for longest arms ever is Yao Defen, who was previously listed as the world's tallest living woman by Guinness World Record before she died in 2012. Yao measured 2 meters (6 feet 7 inches) tall and her arm span was an impressive 2.33 meters (7 feet 8 inches). This means that her arms were almost as long as she was tall!
So, while we cannot definitively say who has the longest arms ever, these two women certainly have some of the longest proportional arm spans in recorded history.