It is very reasonable for me to assume that if $H \leq S_n$ is transitive and $|H|=n$, then $H$ must be generated by a $n$-cycle, but I cannot seem to be able to prove it, so I really can not be sure that it is true. Could you please help me with that? Thank you!
EDIT: Thank you anyone! Could you tell me if we can at least say anything about the group being abelian? How about solvable?
The smallest counterexample is $\{1,(1,2)(3,4),(1,3)(2,4),(1,4)(2,3)\}\leq S_4$.
Indeed, any group of order $n$ is a transitive subgroup of $S_n$ by Cayley's theorem.