Silylboranes have widespread applications in organic synthesis as versatile silylation reagents, which has inspired interest in studying methods for their synthesis. Silicon-stereogenic optically active silylboranes would allow the introduction of silicon-stereogenic silyl groups into various molecules. However, the synthesis of such silicon-stereogenic silylboranes remains unknown to date. Here, we report the first synthesis of silicon-stereogenic optically active silylboranes via stereospecific Pt(PPh3)4-catalyzed Si–H borylation of silicon-stereogenic hydrosilanes in high yield and perfect enantiospecificity (100% es) with retention of the configuration. Furthermore, the first characterization of silicon-stereogenic silyl-boranes by single crystal X-ray diffraction analysis was reported. This protocol is suitable for the stereospecific synthesis of silicon-stereogenic trialkyl-, dialkylbenzyl-, dialkylaryl-, and diarylalkyl-substituted silylboranes with excellent enantiomeric purity. The utility of the silicon-stereogenic silylboranes is demonstrated in silicon–silicon cross-coupling, transition-metal-catalyzed carbon–silicon bond-forming cross-coupling, and conjugate addition reactions with perfect enantiospecificity (100% es). The absolute configurations of the chiral silicon products were successfully confirmed by single-crystal X-ray diffraction analysis. The established synthetic strategy can be expected to expand the chemical space of silicon-stereogenic optically active organosilicon compounds with potentially interesting properties.