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Quantum fluctuations are ubiquitous in physics. Ranging from conventional examples like the harmonic oscillator to intricate theories on the origin of the universe, they alter virtually all aspects of matter -- including superconductivity, phase transitions and nanoscale processes. As a rule of thumb, the smaller the object, the larger their impact. This poses a serious challenge to modern nanotechnology, which aims total control via atom-by-atom engineered devices. In magnetic nanostructures, high stability of the magnetic signal is crucial when targeting realistic applications in information technology, e.g. miniaturized bits. Here, we demonstrate that zero-point spin-fluctuations are paramount in determining the fundamental magnetic exchange interactions that dictate the nature and stability of the magnetic state. Hinging on the fluctuation-dissipation theorem, we establish that quantum fluctuations correctly account for the large overestimation of the interactions as obtained from conventional static first-principles frameworks, filling in a crucial gap between theory and experiment [1,2]. Our analysis further reveals that zero-point spin-fluctuations tend to promote the non-collinearity and stability of chiral magnetic textures such as skyrmions -- a counter-intuitive quantum effect that inspires practical guidelines for designing disruptive nanodevices.