To simplify \( 81^{1/4} \), we can start by rewriting 81 as a power of 3:
\[ 81 = 3^4 \]
Now we can substitute this into the expression:
\[ 81^{1/4} = (3^4)^{1/4} \]
Using the power of a power property \((a^m)^n = a^{m \cdot n}\), we have:
\[ (3^4)^{1/4} = 3^{4 \cdot \frac{1}{4}} = 3^1 = 3 \]
Thus, the simplification of \( 81^{1/4} \) is:
\[ \boxed{3} \]