Lipid and fatty acid profiles provide nutritional information of marine algae, but the analysis of algal fatty acid composition has also been proposed as a chemotaxonomic tool. Although the total lipid (TL) content of macroalgae is usually only 1-6% dry weight (DW), much lower than in microalgae, some species can accumulate interesting long-chain polyunsaturated fatty acids (LC-PUFA) which are essential fatty acids, not produced by humans or animals, that show beneficial health effects. This study aimed to evaluate the lipid and fatty acid profiles of three Brazilian seaweeds, Sargassum vulgare (Ochrophyta), Palisada flagellifera (Rhodophyta), and Ulva fasciata (Chlorophyta) collected from the north-east of Brazil at two seasons (dry and rainy). Lipid and fatty acid profiles in the three macroalgae were stable across seasons. The total fatty acid (TFA) contents of S. vulgare and U. fasciata ranged from 1.3 to 1.5% DW, with the main fatty acids represented by palmitic and oleic acids; however, there was no large accumulation of LC-PUFA. By contrast, P. flagellifera exhibited a lower TFA content (0.8-0.9% DW), but eicosapentaenoic and arachidonic acids accounted for 15-16% and 16-20% of TFA, up to 1.5 and 1.9 mg g-1 DW, respectively. In all species, glycolipids were the most abundant lipid class (60-70%), followed by phospholipids (10-25%), and neutral lipids (10-15%). The composition of each lipid fractions demonstrated that fatty acid profiles of each lipid class were highly species-specific, and lipid profiles were indicative of tropical species. Based on these algae lipid profiles, P. flagellifera could be considered a good source of omega-3 (LC-PUFA). The seasonal stability in the lipid content and fatty acid profiles confers a strong advantage for potential exploitation of those species in the north-eastern regions of Brazil, representing a source of algal biomass with constant biochemical composition all year-round.