PK91 is an attractive folding stool designed by Poul Kjærholm for Fritz Hansen in 1961. The stool has a pared-down design, with a simple seat in canvas or leather attached to an x-shaped base in satin-brushed stainless steel. The seat is available in several colors.

In designing PK91, Kjærholm has combined his great interest in historical furniture with his own modern craftsmanship and artistic expression. The inspiration behind PK91 comes from the stools of ancient Egypt, whose history stretches back to around 1500 BC. PK91 has become one of Kjærholm's great classics and is part of the permanent collection at the Röhsska Museum in Gothenburg.