An interpretation of quantum mechanics that—as far as I understand—is an extension of the Copenhagen interpretation, with the main difference being that it rejects the notion of a single physical reality that is independent of the observer. Each observer, it seems to go, experiences its own Everett branch. This resolves the measurement problem.
The main difference between it and Many Worlds seems to be that Everett branches are indexed by observers rather than possibilities. In other words, observers do not split. From this it seems to me that it follows that Everett branches cannot diverge under Relational Quantum Mechanics; as soon as two observers interact with each other, their realities must synchronize, which puts constraints on the set of possible histories.
To put it in terms of Schrödinger’s Cat: If the cat survives according to its own experience, then the physicist who opens its box must find it alive. This is not true under Many Worlds, where there will be copies of the physicist who find it alive and those who find it dead.
Personally speaking, as far as Copenhagen-based interpretations go, this one seems at least not quite so insane.
I still find Many Worlds (plus decoherence) more intuitive, though.