寇斯猜想（英语：Coase conjecture），又译为科斯猜想、高斯猜想，由经济学家罗纳德·寇斯于1972年提出的垄断理论假说。这个假说的情境是，一个以销售耐久财为主的垄断厂商，他销售的商品不能在市场中再转卖；以及一群有不同价值观的消费者。这个假说的前提是，这个垄断厂商无法得知每一个消费者个别的价值观，因此无法区分出不同的顾客群，在不同时期中用不同价格去贩售他的商品。

在以上情况成立时，寇斯猜想推断，随着时间过去，这个垄断厂商将需要跟自己的已销售出去的商品作价格竞争，因此将会被迫降低售价。

The Coase conjecture, developed first by Ronald Coase, is an argument in monopoly theory. The conjecture sets up a situation in which a monopolist sells a durable good to a market where resale is impossible and faces consumers who have different valuations. The conjecture proposes that a monopolist that does not know individuals' valuations will have to sell its product at a low price if the monopolist tries to separate consumers by offering different prices in different periods. This is because the monopoly is, in effect, in price competition with itself over several periods and the consumer with the highest valuation, if he is patient enough, can simply wait for the lowest price. Thus the monopolist will have to offer a competitive price in the first period which will be low. The conjecture holds only when there is an infinite time horizon, as otherwise a possible action for the monopolist would be to announce a very high price until the second to last period, and then sell at the static monopoly price in the last period. The monopolist could avoid this problem by committing to a stable linear pricing strategy or adopting other business strategies.