核幔边界（英语：core–mantle boundary, CMB）是地核与地函的交界；人们将这个界面称为古登堡界面（Gutenberg discontinuity），或称为古氏不连续面。

1914年，德国地球物理学家宾诺·古登堡（Beno Gutenberg）发现地下2885千米处地震波的传播速度有明显变化，其中纵波的速度明显下降，横波完全消失。后来证实这里是地核与地幔的分界层。

The core–mantle boundary (CMB in the parlance of solid earth geophysicists) of the Earth lies between the planet's silicate mantle and its liquid iron-nickel outer core. This boundary is located at approximately 2880 km (1798 mi) depth beneath the Earth's surface. The boundary is observed via the discontinuity in seismic wave velocities at that depth. This discontinuity is due to the differences between the acoustic impedances of the solid mantle and the molten outer core. P-wave velocities are much slower in the outer core than in the deep mantle while S-waves do not exist at all in the liquid portion of the core. Recent evidence suggests a distinct boundary layer directly above the CMB possibly made of a novel phase of the basic perovskite mineralogy of the deep mantle named post-perovskite. Seismic tomography studies have shown significant irregularities within the boundary zone and appear to be dominated by the African and Pacific LLSVPs (Large Low Shear Velocity Provinces).