  Novae are the observable outcome of a transient thermonuclear runaway on the
surface of an accreting white dwarf in a close binary system. Their high peak
luminosity renders them visible in galaxies out beyond the distance of the
Virgo Cluster. Over the past century, surveys of extragalactic novae,
particularly within the nearby Andromeda Galaxy, have yielded substantial
insights regarding the properties of their populations and sub-populations. The
recent decade has seen the first detailed panchromatic studies of individual
extragalactic novae and the discovery of two probably related sub-groups: the
'faint-fast' and the 'rapid recurrent' novae. In this review we summarise the
past 100 years of extragalactic efforts, introduce the rapid recurrent
sub-group, and look in detail at the remarkable faint-fast, and rapid
recurrent, nova M31N 2008-12a. We end with a brief look forward, not to the
next 100 years, but the next few decades, and the study of novae in the
upcoming era of wide-field and multi-messenger time-domain surveys.
