Hydrodynamic methods of generating and diagnosing dense plasmas with strong interparticle interaction are reviewed. Experiments in shock and isentropic compression of matter to produce Boltzmann and degenerate plasma with maximum pressures in the tens of megabars are discussed. A method for isentropic expansion of metals that have been compressed by strong shock waves, which makes it possible to investigate a broad range of the phase diagram, including the high-temperature boiling curve and the neighborhood of the critical point, is described. The experimental schemes and designs of compressed-air and explosion-type nonideal-plasma generators and the diagnostic tools used are discussed. The results of experiments with nonideal plasmas are reported, and the influence of the interparticle interaction on the thermodynamic, electrophysical, and optical properties of the strongly compressed plasma is analyzed on the basis of theoretical models. The properties of ultrahigh-pressure plasmas and prospects for laser electrodynamic and electroexplosive methods of generating strong shock waves in condensed media are discussed.