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The earth is undergoing its sixth mass extinction event. This biodiversity crisis is directly attributable to anthropogenic disruptions of ecosystem processes. These disruptions include extracting and killing organisms, clearing habitat, introducing exotic species and disrupting climate at a global-scale. Connectivity is an attribute of both populations and ecosystems which, when disrupted, leads to fragmentation. Fragmented systems often have lower ecological functioning and resilience than connected systems. The maintenance of natural rates of ecological connectivity is a major challenge. Mangroves are intertidal forests which grow along the subtropical and tropical coasts of the world. These forests are extremely valuable; maintaining coastal water quality, protecting shorelines from severe weather events, providing habitat for fisheries species and iconic megafauna, and sequestering blue carbon. Unfortunately, mangrove forests also remain vulnerable to the many human activities competing for space in the coastal zone, and to the effects of sea-level rise (SLR). One of the keys to ensuring mangrove conservation and functioning into the future is a thorough understanding of the connectivity and fragmentation of these systems. This thesis consists of four studies. The first is a comprehensive review of research on marine population connectivity. This study identified that intertidal wetlands are particularly under-represented in the marine connectivity literature. This chapter led to the remaining three chapters which assess fragmentation and connectivity in mangroves. The first of these is a mark-recapture experiment which considers connectivity at the population level. I modelled intra-forest dispersal of mangrove propagules as the interaction between propagule and habitat attributes. I identified interactions and thresholds that determine the capacity for propagules to disperse efficiently. The other two chapters consider mangrove fragmentation at a landscape level. The first of these is an assessment of mangrove fragmentation at a global-scale. I identified regions where loss and fragmentation occur as well as how the dominant land-use change in a region mediates the relationship between loss and fragmentation. In the final chapter, I projected the gain, loss and changing connectivity of mangrove and saltmarsh habitats in southeast Queensland, Australia, given a range of SLR and development scenarios. In this chapter I identify how geographic attributes of coastal regions mediate wetland resilience and vulnerability to climate change scenarios, and demonstrate the threat of SLR to both mangrove and saltmarsh habitats in southeast Queensland. This thesis uses a collection of related chapters to address fragmentation and connectivity in mangroves. My intention is to promote further research into the previously under-studied topic of ecological impacts of fragmentation in mangroves.