<p>According to recent studies on sliding/moire ferroelectricity, most 2D van der Waals nonferroelectric monolayers can become ferroelectric via multilayer stacking. In this paper, we propose that a similar strategy can be used to induce desirable van der Waals altermagnetism with symmetry-compensated collinear magnetic orders and non-relativistic spin splitting. Our first-principles calculations show the pervasive co-existence of sliding ferroelectricity and altermagnetism in a series of magnetic multilayers with antiparallel stacking configurations. Upon a twist angle in bilayers, moire ferroelectricity can be combined with altermagnetism, while some untwisted bilayers with zero net magnetizations exhibit non-relativistic spin splittings coupled with sliding ferroelectricity. Our study significantly expands the scope of altermagnetism, and its combination with sliding/moire ferroelectricity brings in new physics as well as promising applications, which should stimulate further experimental efforts.</p>