Hot dense plasmas are a critical state of matter found extensively in inertial confinement fusion and stellar interiors. Their ionization balance and charge-state distribution are largely governed by electron impact ionization (EII)—a fundamental atomic process that also determines the radiative opacity, energy transport, and equation of state of the plasma. Systematic studies of EII under such extreme conditions provide essential atomic data for high-energy-density physics and support the development of diagnostic techniques for probing electronic structure. Unlike low-density ideal plasmas, hot dense plasmas exhibit strong coupling effects that can significantly alter atomic energy levels and wave functions. These modifications shift ionization thresholds and change EII cross sections, thereby limiting the predictive power of plasma simulations and undermining the reliability of experimental diagnostics. To address these challenges, this review provides a comprehensive overview of recent international progress in EII research in hot dense plasmas. Particular emphasis is placed on the self-consistent description of atomic structure within the ion correlation model using the hypernetted-chain (HNC) approximation, as well as on the evaluation of EII cross sections via the distorted-wave (DW) approximation. Key findings include the following: for ionization potential depression (IPD), the two-step model aligns more closely with the Stewart-Pyatt (SP) model under weak coupling, but agrees better with the Ecker-Kröll (EK) model in the strong-coupling regime. For EII cross sections, the Debye-Hückel model yields the strongest screening and the largest cross sections, followed by the ion-sphere model and then the ion-correlation model. In addition, the momentum relaxation effect is found to enhance EII cross sections by up to an order of magnitude and thus cannot be overlooked. The review also discusses recent advances and key challenges, and provides an outlook on promising directions for future research.