The ysalamiri (singular ysalamir) are a species of arborial, non-sapient, salamander-like creatures native to the planet Myrkr in the Star Wars EU. They first appear in the Heir to the Empire series of novels by Timothy Zahn.
Ysalamiri have the unusual ability to project a Force-neutral sphere around themselves within which the Force's effects on the physical world are minimal. The effects of multiple ysalamiri are cumulative, so two ysalamiri in close proximity create a larger, combined bubble of Force suppression. The effect of the many ysalamiri on Myrkr is so strong that their combined Force-neutral bubble extends to the edge of the planet's atmosphere.
Ysalamiri can grow to over a meter in length, but a typical specimen is approximately 50 cm long, easily light enough for a man to carry. Keeping them in captivity requires the construction of scaffolding to simulate their arborial habitat, but even a small scaffold that can be worn as a backpack will suffice.
Captured ysalamiri have several practical applications, chief among them nullifying the powers of Jedi (or Sith). As well, by nullifying the Force connection between clones and their original tissue donors, they allow the clones to grow to maturity rapidly without going insane. Grand Admiral Thrawn exploited both uses of ysalamiri during his campaign against the New Republic.