Wrought Ni-based superalloys are widely used in aviation and energy fields because of their excellent creep resistance, thermal stability, heat corrosion resistance, and oxidation resistance at high temperatures. The mechanical properties of wrought Ni-based superalloys are significantly affected by grain boundary precipitation. Among the grain boundary second phases, the topologically close-packed (TCP) phase is usually discovered in wrought superalloys with the addition of refractory metal elements. As a complex intermetallic compound with only tetrahedral interstices, the TCP phase is stacked with a high packing density of atoms, embodying low plasticity and high brittleness. Given these characteristics, the TCP phase tends to promote crack initiation and propagation during creep, thereby reducing the alloy's creep strength. Additionally, the formation of the TCP phase requires several refractory elements, thereby weakening the effect of the solid solution strengthening of the matrix. As a ubiquitous TCP phase in wrought superalloys, μ phases are represented by rectangular and parallelogram structural subunits, which are parallel to the basal plane of μ phases. Basal stacking faults (SFs) are the most common defects in the μ phase, and SFs with different stacking sequences will form different phases with corresponding structures and mechanical properties. The μ phases and their basal SFs in wrought Ni-based superalloy GH4151 were systematically studied by multifarious electron microscopy techniques, such as EDS and atomic-resolution high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) of aberration-corrected TEM, revealing the structure and composition of the μ phase and the structure and distribution of numerous basal SFs in the μ phase. Based on the different arrangements of structural subunits, the basal SFs were divided into four types. Type I basal SF is equivalent to the μ phase with a layer of parallelogram structural subunit reversing to form two layers of microsymmetric structures, the reversed parallelogram structural subunit is symmetrical to the rectangular one; type II basal SF is equivalent to type I basal SF in the absence of a layer of the rectangular structural subunit, forming a C14 structure and microsymmetric structure; type III basal SF results from the absence of a layer of the parallelogram structural subunit in the μ phase, forming a complete Zr₄Al₃ phase; and type IV basal SF results from the absence of a layer of the rectangular structural subunit in the μ phase, forming a C15 structure. Among the four types of basal SFs, type II and type IV basal SFs form Laves phases, but the occurrence of the former is more than that of the latter. This finding is related to the stability of type II basal SF (C14 structure) over type IV basal SF (C15 structure) revealed by the first-principle calculations.