  We propose two types of topologically stable knot solitons in condensed
matters, one in two-component Bose-Einstein condensates and one in two-gap
superconductors. We identify the knot in Bose-Einstein condensates as a twisted
vorticity flux ring and the knot in two-gap superconductors as a twisted
magnetic flux ring. In both cases we show that there is a remarkable interplay
between topology and dynamics which transforms the topologcal stability to the
dynamical stability, and vise versa. We discuss how these knots can be
constructed in the spin-1/2 condensate of $^{87}{\rm Rb}$ atoms and in two-gap
superconductor of $MgB_2$.
