That move should mean owners of the hardware in other markets will see the Marshmallow update arrive soon.
As usual, it's taken several months for handset makers to release the latest version of Android. As of January 4, Marshmallow accounted for a tiny 0.7 percent of all devices connecting to Google Play. However, with Samsung rolling it out now to its flagships, that figure should rise in coming weeks and months.
LG, the company behind Google's Nexus 5X, announced back in October that it had started rolling out Marshmallow to its G4. But that upgrade was limited to users in Poland.
It hasn't announced further markets yet and as recently as two weeks ago launched new mid-range K Series handsets that ship with Android Lollipop.
Sony has announced Marshmallow will be available for its Z5 range and other Xperia devices, but the company has not said when the update will arrive. Its most recent updates have brought certain Xperia devices up to date with Google's January security patches for Android.