I am interested in regular graphs $G$ such that for each pair of 1-factors (=perfect matchings) $F$ and $F'$ there is an automorphism of $G$ that takes $F$ to $F'$. Let's call this property ***matching transitivity***. Those graphs should have a fairly big automorphism group. **I am wondering whether it is possible to characterize them.** Trivial examples of matching-transitive graph are $K_{2n}$ or the complete bipartite graph $K_{n,n}$. ***EDITED** after Brendan McKay's comment*: If we remove successively 1-factors from such a graph, it is <strike>clear</strike> *not true* that this property is maintained at each stage. The question is inspired by the existence of graphs whose 2-factors are isomorphic (as graphs), i.e. all have the same partition $\pi$ as cycle type. For a discussion and examples of such graphs for various cycle types see [here][1] and [here][2]. All those graphs are cubic, and BTW I don't think that such a graph can be $k$-regular with $k>3$. (Is there an easy argument for that?) Some of those graphs have lots of symmetries, others a rather small automorphism group, like for instance, the graph of type $(5,11)$ given in [this answer][3], which has a unique triangle and automorphism group $S_3$, but not less than $12$ different 1-factors (so it cannot be matching-transitive). On the other hand, the [Heawood graph][4] ($|Aut(G)|=336$) is, and so is the [Coxeter Graph][5] (same automorphism group) as outlined [here][6]. **EDIT**: As mentioned in another comment, there are many graphs with a unique perfect matching, which is obviously not what I am after. So I'll add the (somewhat mild) condition that each edge should belong to some perfect matching. Such a graph is called *$1$-extendable* (cf. page 113 in [László Lovász, *Matching Theory*, Annals of Discrete Mathematics 29, North-Holland, 1986, ISBN: 0 444 87916 1]). So: > For given $n$ and $k$, can anything be said about the matching-transitivity of a connected $1$-extendable $k$-regular graph on $n$ vertices in terms of the size (or structure) of its automorphism group? Note that both Heawood and Coxeter Graph are indeed $1$-extendable, and so is the $(5,11)$ graph mentioned before. There is possibly more hope now that, roughy speaking, the bigger the automorphism group, the bigger the chance for the graph to be matching-transitive. [1]: https://mathoverflow.net/questions/177625/cubic-graphs-whose-2-factors-all-have-the-same-cycle-type [2]: https://mathoverflow.net/questions/180299/more-3-connected-cubic-graphs-with-all-2-factors-of-same-cycle-type [3]: https://mathoverflow.net/a/177832/29783 [4]: https://en.wikipedia.org/wiki/Heawood_graph#Combinatorial_properties [5]: http://mathworld.wolfram.com/CoxeterGraph.html [6]: https://www.famnit.upr.si/files/files/seminarji/coxeterpresentation-Anna%20Klymenko.pdf