Deterministic Gaussian approximations of intractable posterior distributions are common in Bayesian inference. From an asymptotic perspective, a theoretical justification in regular parametric settings is provided by the Bernstein-von Mises theorem. However, such a limiting behavior may require a large sample size before becoming visible in practice. In fact, in situations with small-to-moderate sample size, even simple parametric models often yield posterior distributions which are far from resembling a Gaussian shape, mainly due to skewness. In this article, we provide rigorous theoretical arguments for such a behavior by deriving a novel limiting law that coincides with a closed-form and tractable skewed generalization of Gaussian densities, and yields a total variation distance from the exact posterior whose convergence rate can be shown to be of order 1/n, up to a logarithmic factor. Such a result provides a substantial accuracy improvement over the classical Bernstein-von Mises theorem whose convergence rate, under similar conditions, is of order 1/ √ n, again up to a logarithmic factor. In contrast to higher-order approximations based on, e.g., Edgeworth expansions, which require finite truncations for inference, possibly leading to even negative densities, our theory characterizes the limiting behavior of Bayesian posteriors with respect to a sequence of valid and tractable densities. These advancements further motivate a practical plug-in version which replaces the unknown model parameters with the corresponding maximum-a-posteriori estimate to obtain a novel skew-modal approximation achieving the same improved rate of convergence of our skewed Bernstein-von Mises theorem. Extensive simulations and a real-data application confirm that our new theory closely matches the empirical behavior observed in practice even in finite, possibly small, sample regimes. The proposed skew-modal approximation further exhibits improved accuracy not only relative to classical Laplace approximation, but also with respect to state-of-the-art Gaussian and non-Gaussian approximations from mean-field variational Bayes and expectation-propagation.* Co-funded by the European Union (ERC, BigBayesUQ, project number: 101041064). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Research Council. Neither the European Union nor the granting authority can be held responsible for them.