Flax–gypsum composites are an emerging class of environmentally friendly materials that combine the mechanical properties of gypsum with the advantageous characteristics of flax fibers. The production of flax–gypsum composites involve the incorporation of flax fibers, derived from the flax plant, into gypsum matrix systems. In order to create a uniform distribution of fibers within the gypsum matrix, the hand lay-up approach has been used to produce the specimens. The fiber content and orientation significantly influence the resulting mechanical and physical properties of the composites. Various tests were conducted on the samples, such as a flexural test, a compression test, a density test, a water absorption test, and a microscopy test. The addition of flax fibers imparts several desirable properties to the gypsum matrix. When combined with gypsum, these fibers enhanced the composite’s mechanical properties, such as flexural strength and compressive strength. The results indicated improved compression and flexural strengths due to effective load transfer within the matrix, for up to 10% of fiber loading. A decrease in composite density upon flax fiber addition results in a lighter material, enabling insights for various applications.