Which among the following is the oldest dynasty?

Looking at the historical chronology of the given dynasties:
* Maurya Dynasty: Founded by Chandragupta Maurya (c. $322\text{–}185\text{BCE}$).
* Kanva Dynasty: Founded by Vasudeva Kanva (c. $73\text{–}28\text{BCE}$).
* Kushan Dynasty: Prominent during the $1^{\text{st}}\text{ to }{3}^{\text{rd}}$ centuries $\text{CE}$.
* Gupta Dynasty: Founded by Sri Gupta (c. $319\text{–}550\text{CE}$).
Therefore, the Maurya dynasty is the oldest among the options.