Polymer Mediated Phase Stability of Colloids Colloid–polymer mixtures are subject of intensive research due to their wide range of applicability for instance in coatings and food stuffs. This thesis constitutes a fundamental investigation towards a better control over the stability of such suspensions. Through the chapters different key parameters governing the stability of colloid–polymer mixtures are explored. How the colloid (pigment) shape and the effective polymer colloid affinity modulate the stability of the suspension are examples of these key parameters. Despise the mostly theoretical results presented the thesis is written in a format accessible to a broad scientific audience. Some of the equations of state presented might of direct use to experimentalists. Furthermore new theoretical insights about colloid–polymer mixtures are put forward. These include four phase coexistences in effective two component quantification of depletant partitioning at high colloidal concentrations multiple re entrant phase behaviour of the colloidal fluid–solid coexistence and a condition where polymers are neither depleted nor adsorbed from to the colloidal surface Introduction Part 1: Spherical Colloids Tuning the Phase Diagram of Colloid–polymer Mixtures Depletion driven Solid–solid Coexistence in Colloid–polymer Mixtures Unipletion in Colloid–polymer Mixtures Part 2: Anisotropic Hard Colloids Superballs Mixed with Non Adsorbing Polymers Discotic Dispersions Mediated by Depletion Part 3: Spherical Association Colloids On the Colloidal Stability of Association Colloids Polymer mediated Stability of Micellar Suspensions