To evaluate the function \( f(x) = -2x - 5 \) for \( x = 3 \), you can substitute \( 3 \) into the function:
\[ f(3) = -2(3) - 5 \]
Calculate \( -2(3) \):
\[ -2(3) = -6 \]
Now substitute this value back into the function:
\[ f(3) = -6 - 5 \]
Finally, perform the subtraction:
\[ -6 - 5 = -11 \]
Thus, the value of \( f(3) \) is \( -11 \).
The answer is \( \boxed{-11} \).