Mullite (3Al 2 O 3 Á2SiO 2 ) is well-known as superior engineering ceramic materials owing to its relatively high chemical stability, good refractory properties, high temperature mechanical strength, and low thermal expansion coefficient. [1,2] Fabrication of continuous mullite nanofibers is highly desired because it is an important candidate used as reinforcement of metals, ceramics, and resins. [3,4] Several traditional methods such as sol-gel, melt spinning, and solution spinning methods have been used to fabricate mullite fibers. [5][6][7] Electrospinning is a promising technique that utilizes electric forces along to drive the spinning process and to produce fibers. Unlike sol-gel fabricated nanofibers, most of which contain foreign cations as catalysts and require further expensive purification, electrospun nanofibers are more pure, inexpensive, continuous, and relatively easy to align, assemble, and process into applications. [8][9][10][11] Unlike conventional spinning techniques (e.g., melt spinning and solution spinning methods) that are capable of producing fibers with diameters in the micrometer range ($5-15 mm), electrospinning is capable of producing fibers with diameters in the nanometer range ($50-1000 nm) with less cracks. In the recent decade, numerous electrospun ceramic nanofibers including silica, titania, and zirconia, have been fabricated and studied throughout the world. [12][13][14] However, very little literatures have been reported about electrospinning approach fabricating mullite nanofibers due to its more complicated stoichiometry/microstructure and relatively higher synthesis temperature. Recnetly, Dharmaraj et al. have reported the fabrication of electrospun mullite nanofibers, which focused on the sintering process, studying the effect of calcination temperature on the morphology evolution of mullite nanofibers. [15] However, much less attention has been paid to the electrospinning process.In the present work, electrospinning method is introduced to fabricate mullite nanofibers. Three different solvent systems including de-ionized water (DI) (solution A), DI/ absolute alcohol (EtOH) (solution B), and DI/N, N-dimethylformamide (DMF) (solution C) were used to prepare precursor spinning solutions. The effect of different solvents on the micromorphological evolution, crystallization sequence, and structural properties of both the as-electrospun fibers and the final sintered mullite nanofibers will be primarily focused and systematically investigated.