Microalgae are a diverse group of photosynthetic organisms recognized for their potential to sustainably produce natural metabolites, including pigments, vitamins, proteins, carbohydrates, lipids, and biofuels. Their rapid growth, low nutritional requirements, and ability to grow on non-arable land and wastewater support their application in energy, agriculture, pharmaceuticals, and nutraceuticals. While previous research has explored the influence of environmental factors on microalgal metabolism, limitations remain due to the intrinsic genetic capacities of these organisms. Genetic engineering enables targeted modification of metabolic pathways, addressing these constraints. Although various gene-editing tools, including CRISPR-Cas9, ZFNs, TALENs, and RNA interference (RNAi), are available, their application in microalgae remains limited. This chapter reviews current strategies to enhance microalgal productivity through gene editing, synthetic biology, promoter engineering, gene overexpression, transcription factor engineering, high-throughput screening, and omics-based methods. Challenges associated with profitable biomass production persist, but recent developments provide a foundation for further expansion in microalgal biotechnology.