Albert Einstein primarily studied physics. He is renowned for his groundbreaking work in theoretical physics, particularly his theory of relativity, which revolutionized our understanding of space, time, gravity, and the universe.

While he focused on physics, he also had a strong interest in mathematics, which was essential for his theoretical work. He also had some exposure to philosophy, particularly through his interactions with other scientists and intellectuals.

However, his main area of study and expertise was physics.