Apicomplexan parasites are pathogens responsible for major human diseases such as toxoplasmosis caused by and malaria caused by spp. Throughout their intracellular division cycle, the parasites require vast and specific amounts of lipids to divide and survive. This demand for lipids relies on a fine balance between de novo synthesized lipids and scavenged lipids from the host. Acetyl-CoA is a major and central precursor for many metabolic pathways, especially for lipid biosynthesis. possesses a single cytosolic acetyl-CoA synthetase (ACS). Its role in the parasite lipid synthesis is unclear. Here, we generated an inducible ACS KO parasite line and confirmed the cytosolic localization of the protein. We conductedC-stable isotope labeling combined with mass spectrometry-based lipidomic analyses to unravel its putative role in the parasite lipid synthesis pathway. We show that its disruption has a minor effect on the global FA composition due to the metabolic changes induced to compensate for its loss. However, we could demonstrate that ACS is involved in providing acetyl-CoA for the essential fatty elongation pathway to generate FAs used for membrane biogenesis. This work provides novel metabolic insight to decipher the complex lipid synthesis in.