  Extrasolar debris disks are the dust disks found around nearby main sequence
stars arising from the break-up of asteroids and comets orbiting the stars.
Far-IR surveys (e.g., with Herschel) showed that ~20% of stars host detectable
dust levels. While dust temperatures suggest a location at 10s of au comparable
with our Kuiper belt, orders of magnitude more dust is required implying a
planetesimal population more comparable with the primordial Kuiper belt. High
resolution imaging (e.g., with ALMA) has mapped the nearest and brightest
disks, providing evidence for structures shaped by an underlying planetary
system. Some of these are analogous to structures in our own Kuiper belt (e.g.,
the hot and cold classical, resonant, scattered disk and cometary populations),
while others have no Solar System counterpart. CO gas is seen in some debris
disks, and inferred to originate in the destruction of planetesimals with a
similar volatile-rich composition to Solar System comets. This chapter reviews
our understanding of extrasolar Kuiper belts and of how our own Kuiper belt
compares with those of neighbouring stars.
