Abstract: In effective field theories (EFTs), the potentially unknown high energy physics is encoded into the couplings of higher-derivative interactions. The idea of the S-matrix bootstrap for EFTs is to use fundamental properties, such as unitarity (positivity) and analyticity of the scattering amplitudes, to bound the effective couplings. Not only does this constrain the "landscape" of EFTs, it turns out that it can also be used to determine restrictions on the high energy spectrum of unitary theories. In the talk, I'll introduce the ideas of the bootstrap and give examples of a variety of results, from basic scalars models, to pion- and super Yang-Mills EFTs.