To simplify the expression \( 125^{2/3} \), we first rewrite it in terms of base factors.
First, recognize that \( 125 \) can be expressed as:
\[ 125 = 5^3 \]
Now substituting \( 125 \) in our expression gives us:
\[ 125^{2/3} = (5^3)^{2/3} \]
Using the power of a power property, we multiply the exponents:
\[ (5^3)^{2/3} = 5^{3 \cdot (2/3)} = 5^2 \]
Now, simplify \( 5^2 \):
\[ 5^2 = 25 \]
Thus, the original expression \( 125^{2/3} \) simplifies to:
\[ \boxed{25} \]