Single-cell RNA sequencing (scRNA-seq) has significantly advanced our understanding of melanoma heterogeneity and the underlying mechanisms driving treatment resistance. Melanoma is a heterogeneous disease with distinct subtypes, including cutaneous, mucosal, acral, and uveal melanoma, each with unique biological behaviors and responses to therapy. Cutaneous melanoma, the most common subtype, has seen improvements in treatment and survival due to molecular targeted therapies and immunotherapies. However, treatment resistance remains a major challenge, often attributed to intratumoral heterogeneity (ITH), which refers to the diversity of molecular and phenotypic profiles within a single tumor. This heterogeneity is driven by the plasticity of melanoma cells and the diversity of stromal and immune cells in the tumor microenvironment (TME). ITH contributes to varying treatment responses and resistance, as melanoma cells can transition between distinct phenotypic and transcriptional states, including differentiated and dedifferentiated states. These states are influenced by factors such as MITF expression, and are associated with different levels of invasiveness and treatment responsiveness. Single-cell sequencing technologies have enabled a more detailed analysis of these states, revealing the complexity of melanoma cell diversity and the roles of various immune cell subsets. Treatment resistance in melanoma is often due to the activation of alternative signaling pathways or mutations in drug targets, and can be intrinsic or extrinsic to the tumor. Intrinsic resistance involves alterations in immune signaling pathways, while extrinsic resistance is related to the tumor microenvironment. scRNA-seq has provided insights into these mechanisms, identifying distinct cell states and their responses to therapies. For example, melanoma cells with a dedifferentiated invasive phenotype are more resistant to BRAF/MEK inhibitors and may show cross-resistance to immunotherapy. scRNA-seq has also revealed the heterogeneity of immune cell populations within melanoma tumors, including T cells and NK cells, and their functional states. These findings highlight the importance of understanding ITH for developing more effective therapies. scRNA-seq has enabled the identification of distinct melanoma cell states and their transcriptional profiles, which are crucial for understanding treatment resistance and improving therapeutic strategies. Despite these advances, challenges remain in translating these findings into clinical applications, as bulk RNA sequencing lacks the resolution to capture the complexity of ITH. Future research should focus on integrating scRNA-seq with other omics approaches to better understand melanoma biology and develop targeted therapies.Single-cell RNA sequencing (scRNA-seq) has significantly advanced our understanding of melanoma heterogeneity and the underlying mechanisms driving treatment resistance. Melanoma is a heterogeneous disease with distinct subtypes, including cutaneous, mucosal, acral, and uveal melanoma, each with unique biological behaviors and responses to therapy. Cutaneous melanoma, the most common subtype, has seen improvements in treatment and survival due to molecular targeted therapies and immunotherapies. However, treatment resistance remains a major challenge, often attributed to intratumoral heterogeneity (ITH), which refers to the diversity of molecular and phenotypic profiles within a single tumor. This heterogeneity is driven by the plasticity of melanoma cells and the diversity of stromal and immune cells in the tumor microenvironment (TME). ITH contributes to varying treatment responses and resistance, as melanoma cells can transition between distinct phenotypic and transcriptional states, including differentiated and dedifferentiated states. These states are influenced by factors such as MITF expression, and are associated with different levels of invasiveness and treatment responsiveness. Single-cell sequencing technologies have enabled a more detailed analysis of these states, revealing the complexity of melanoma cell diversity and the roles of various immune cell subsets. Treatment resistance in melanoma is often due to the activation of alternative signaling pathways or mutations in drug targets, and can be intrinsic or extrinsic to the tumor. Intrinsic resistance involves alterations in immune signaling pathways, while extrinsic resistance is related to the tumor microenvironment. scRNA-seq has provided insights into these mechanisms, identifying distinct cell states and their responses to therapies. For example, melanoma cells with a dedifferentiated invasive phenotype are more resistant to BRAF/MEK inhibitors and may show cross-resistance to immunotherapy. scRNA-seq has also revealed the heterogeneity of immune cell populations within melanoma tumors, including T cells and NK cells, and their functional states. These findings highlight the importance of understanding ITH for developing more effective therapies. scRNA-seq has enabled the identification of distinct melanoma cell states and their transcriptional profiles, which are crucial for understanding treatment resistance and improving therapeutic strategies. Despite these advances, challenges remain in translating these findings into clinical applications, as bulk RNA sequencing lacks the resolution to capture the complexity of ITH. Future research should focus on integrating scRNA-seq with other omics approaches to better understand melanoma biology and develop targeted therapies.