The volume \( V \) of a rectangular prism can be calculated using the formula:
\[ V = \text{Base Area} \times \text{Height} \]
Given that the base area is \( 15 \) square units and the height is \( 5 \) units, we can substitute these values into the formula:
\[ V = 15 , \text{units}^2 \times 5 , \text{units} = 75 , \text{units}^3 \]
Thus, the volume of the rectangular prism is \( 75 \) cubic units.