DNS over TLS (DoT) is a network security protocol for encrypting and wrapping Domain Name System (DNS) queries and answers via the Transport Layer Security (TLS) protocol. The goal of the method is to increase user privacy and security by preventing eavesdropping and manipulation of DNS data via man-in-the-middle attacks. The well-known port number for DoT is 853.

While DNS over TLS is applicable to any DNS transaction, it was first standardized for use between stub or forwarding resolvers and recursive resolvers, in RFC 7858 in May of 2016. Subsequent IETF efforts specify the use of DoT between recursive and authoritative servers ("Authoritative DNS over TLS" or "ADoT") and a related implementation between authoritative servers (Zone Transfer-over-TLS or "xfr-over-TLS").

BIND supports DoT connections as of version 9.17. Earlier versions offered DoT capability by proxying through stunnel. Unbound has supported DNS over TLS since 22 January 2023. Unwind has supported DoT since 29 January 2023. With Android Pie's support for DNS over TLS, some ad blockers now support using the encrypted protocol as a relatively easy way to access their services versus any of the various work-around methods typically used such as VPNs and proxy servers.

Android clients running Android Pie or newer support DNS over TLS and will use it by default if the network infrastructure, for example the ISP, supports it.

In April 2018, Google announced that Android Pie will include support for DNS over TLS, allowing users to set a DNS server phone-wide on both Wi-Fi and mobile connections, an option that was historically only possible on rooted devices. DNSDist, from PowerDNS, also announced support for DNS over TLS in version 1.3.0.

Linux and Windows users can use DNS over TLS as a client through the NLnet Labs stubby daemon or Knot Resolver. Alternatively they may install getdns-utils to use DoT directly with the getdns_query tool. The unbound DNS resolver by NLnet Labs also supports DNS over TLS.

Apple's iOS 14 introduced OS-level support for DNS over TLS (and DNS over HTTPS). iOS does not allow manual configuration of DoT servers, and requires the use of a third-party application to make configuration changes.

systemd-resolved is a Linux-only implementation that can be configured to use DNS over TLS, by editing /etc/systemd/resolved.conf and enabling the setting DNSOverTLS. Most major Linux distributions have systemd installed by default.^{[circular reference]}