邮政蒸汽船（Mail steamer），又称邮政船、邮轮或邮船，是一种运送邮件通过水路的船，例如穿越海洋或各个岛屿，主要盛行于19世纪到20世纪早期，这时寄一封长距离信件的花费下降到一个普通人都能付得起。

除了运载邮件，大部分的邮政船也运载乘客或货物，因为邮政收入并不足以支付航行的成本。

当蒸汽船载运的邮件到达时收取通知会被登在报纸上，这也帮了蒸汽船的载人载货服务打了免费广告。

在大部分的情况，由邮船寄送的邮件抵达时会被送到邮局。有时候，正要送来的邮件会被广告在当地的报纸上通知收件人去邮局或邮船的办公室收件或缴费（若还没支付费用时）。

Packet boats were small boats designed for domestic mail, passenger, and freight transportation in European countries and their colonies, including North American rivers and canals. They were used extensively during the 18th and 19th centuries and featured regularly scheduled service.