We study variants of the local models constructed by the second author and Zhu and consider corresponding integral models of Shimura varieties of abelian type. We determine all cases of good, resp. of semi-stable, reduction under tame ramification hypotheses.Date: March 16, 2020. 1 2 X. HE, G. PAPPAS, AND M. RAPOPORTtwo examples above exhaust all possibilities (this statement has to be interpreted correctly, by considering the natural compactification of the modular curve). This comes down to a statement about the spectral decomposition under the action of the Hecke algebra of the ℓ-adic cohomology of modular curves. Unfortunately, the generalization of this statement to other Shimura varieties seems out of reach at the moment.The other possible interpretation of the question is to ask for good, resp. semistable, reduction of a specific class of p-integral models of Shimura varieties. Such a specific class has been established in recent years for Shimura varieties with level structure which is parahoric at p, the most general result being due to M. Kisin and the second author [30]. The main point of these models is that their singularities are modeled by their associated local models, cf. [40]. These are projective varieties which are defined in a certain sense by linear algebra, cf. [21,47]. More precisely, for every closed point of the reduction modulo p of the p-integral model of the Shimura variety, there is an isomorphism between the strict henselization of its local ring and the strict henselization of the local ring of a corresponding closed point in the reduction modulo p of the local model. Very often every closed point of the local model is attained in this way. In this case, the model of the Shimura variety has good, resp. semi-stable, reduction if and only if the local model has this property. Even when this attainment statement is not known, we deduce that if the local model has good, resp. semi-stable, reduction, then so does the model of the Shimura variety. Therefore, the emphasis of the present paper is on the structure of the singularities of the local models and our results determine local models which have good, resp. semi-stable reduction.Let us state now the main results of the paper, as they pertain to local models. See Section 3 for corresponding results for Shimura varieties, and Section 4 for results on Rapoport-Zink spaces. Local models are associated to local model triples. Here a LM triple over a finite extension F of Q p is a triple (G, {µ}, K) consisting of a reductive group G over F , a conjugacy class of cocharacters {µ} of G over an algebraic closure of F , and a parahoric group K of G. We sometimes write G for the affine smooth group scheme over O F corresponding to K. It is assumed that the cocharacter {µ} is minuscule (i.e., any root takes values in {0, ±1} on {µ}). The reflex field of the LM triple (G, {µ}, K) is the field of definition of the conjugacy class {µ}. One would like to associate to (G, {µ}, K) a local model M loc K (G, {µ}), a flat projective scheme over the ring...