Elon Musk vs Jeff Bezos: A History of Their Twitter Feud

Elon Musk and Jeff Bezos, two of the world's most prominent CEOs, have had a simmering rivalry for the last 15 years.

The two executives have sparred over their respective space ambitions — Musk runs SpaceX, while Bezos owns Blue Origin — but it hasn't stopped there: Musk has called Bezos a copycat over Amazon's satellite plans, as well as criticized the company's business practices. In response, both Amazon and Blue Origin have filed formal protests and lawsuits regarding SpaceX-related issues.

Musk and Bezos are two of the world's most powerful executives. Bezos is the world's wealthiest person and recently stepped down as CEO of Amazon's sprawling empire; at the same time, he's becoming more involved than ever in Blue Origin, even taking a ride on one of his own rockets. Musk, for his part, is a dual CEO, steering the ship at both Tesla and SpaceX.

Their not-so-subtle rivalry has even led to Twitter spats and name-calling — and things only appear to be getting worse.

Here's how Musk and Bezos' feud began, and what's happened since.