To simplify the expression \(5^{10} \cdot 5^5\) using the Product Rule of Exponents, we apply the rule which states that \(a^m \cdot a^n = a^{m+n}\).
In this case:
\[ 5^{10} \cdot 5^5 = 5^{10 + 5} = 5^{15} \]
Thus, the simplified form of \(5^{10} \cdot 5^5\) is \(5^{15}\).