Cytokinesis and septation in fungi play an essential role in development. The molecular basis of septation and cytokinesis is well known for the model unicellular yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe. In unicellular fungi, cytokinesis leads to the physical separation of cells. In multicellular fungi, however, septation divides hyphal compartments but allows cytoplasmic continuity. There is a conservation in the canonical steps leading to cytokinesis and septation, which are tightly controlled by a signalling cascade called Septation Initiation Network (SIN), in the case of S. pombe, and Mitosis Exit Network (MEN) in the case of S. cerevisiae. Filamentous fungi grow via polarised hyphal elongation, which requires septation for maintaining structural integrity; however, they can switch to isotropic growth by cytoskeletal remodelling, leading to cell shape changes. In pathogenic filamentous fungi, this has relevant importance because the development of infection-related structures is tightly linked with polarity changes, as well as with nuclear division. This is the case for one of the most devastating filamentous fungi, called the rice blast fungus Magnaporthe oryzae. M. oryzae produces tricellular spores, which contain two septa and three nuclei. The spores, upon specific physical and nutritional cues, undergo the formation of an infection structure called appressorium. Septin-mediated actin remodelling at the base of the appressorium is essential for repolarisation at the base of the appressorium and the production of invasive hyphae that colonise the host tissue. During appressorium development, a round of mitosis occurs in the apical cell of the spore, which is essential for appressorium-mediated infection. Cell cycle progression is tightly linked to infection-related morphogenesis, where transitions between isotropic and polarised growth states are coordinated with nuclear division and septation machinery. Addressing key questions about the precise signals that determine septum placement and timing, and how cell cycle checkpoints regulate septin dynamics during appressorium development will advance our understanding of fungal pathogenesis and potentially reveal targets for antifungal strategies. In this chapter, we explore the role of septation and cytokinesis in pathogenic filamentous fungi. We explain in detail the molecular basis of septation and cytokinesis for the model unicellular yeasts S. pombe and S. cerevisiae, as well as for model filamentous fungi Aspergillus nidulans and Neurospora crassa, to then focus on the plant pathogen M. oryzae, the causal agent of blast disease that is a threat to global food security. In this review, we highlight the importance of septins for appressorium development and cell cycle control on septation and cytokinesis. Finally, we consider the broader implications and future research directions for appressorium-forming pathogenic fungi.