The fatty acid component of commodity soybean seeds typically consists of approximately 12-15% saturated fatty acids in the form of palmitic acid and stearic acid. An important goal in soybean breeding is the reduction of saturated fats, in order to produce healthier vegetable oils for food applications. Genetic approaches have been instrumental in reducing levels of palmitic acid, which is the most abundant saturated fat in soybean seeds. In this study we describe a new mutant allele of the FATB1a gene that encodes a palmitoyl-acyl carrier protein thioesterase. The mutation is expected to result in early termination of the FATB1A protein and mutant seeds carrying this allele contain 5.5% palmitic acid. This new allele can be introduced into conventional soybean lines, alone or in combination with other modifications to generate soybean lines with improved oil composition.