diff --git a/nixos/doc/manual/configuration/configuration.xml b/nixos/doc/manual/configuration/configuration.xml
index afffd60bc48..1e488b59343 100644
--- a/nixos/doc/manual/configuration/configuration.xml
+++ b/nixos/doc/manual/configuration/configuration.xml
@@ -26,6 +26,7 @@ effect after you run <command>nixos-rebuild</command>.</para>
 
 <!-- FIXME: auto-include NixOS module docs -->
 <xi:include href="postgresql.xml" />
+<xi:include href="acme.xml" />
 <xi:include href="nixos.xml" />
 
 <!-- Apache; libvirtd virtualisation -->
diff --git a/nixos/doc/manual/default.nix b/nixos/doc/manual/default.nix
index 844cba57cd8..bd558dac971 100644
--- a/nixos/doc/manual/default.nix
+++ b/nixos/doc/manual/default.nix
@@ -55,6 +55,7 @@ let
       cp -prd $sources/* . # */
       chmod -R u+w .
       cp ${../../modules/services/databases/postgresql.xml} configuration/postgresql.xml
+      cp ${../../modules/security/acme.xml} configuration/acme.xml
       cp ${../../modules/misc/nixos.xml} configuration/nixos.xml
       ln -s ${optionsDocBook} options-db.xml
       echo "${version}" > version
diff --git a/nixos/modules/module-list.nix b/nixos/modules/module-list.nix
index 9b25f998400..5c1cde98d3d 100644
--- a/nixos/modules/module-list.nix
+++ b/nixos/modules/module-list.nix
@@ -80,6 +80,7 @@
   ./programs/xfs_quota.nix
   ./programs/zsh/zsh.nix
   ./rename.nix
+  ./security/acme.nix
   ./security/apparmor.nix
   ./security/apparmor-suid.nix
   ./security/ca.nix
diff --git a/nixos/modules/security/acme.nix b/nixos/modules/security/acme.nix
new file mode 100644
index 00000000000..8f3a2ee073b
--- /dev/null
+++ b/nixos/modules/security/acme.nix
@@ -0,0 +1,202 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+
+  cfg = config.security.acme;
+
+  certOpts = { ... }: {
+    options = {
+      webroot = mkOption {
+        type = types.str;
+        description = ''
+          Where the webroot of the HTTP vhost is located.
+          <filename>.well-known/acme-challenge/</filename> directory
+          will be created automatically if it doesn't exist.
+          <literal>http://example.org/.well-known/acme-challenge/</literal> must also
+          be available (notice unencrypted HTTP).
+        '';
+      };
+
+      email = mkOption {
+        type = types.nullOr types.str;
+        default = null;
+        description = "Contact email address for the CA to be able to reach you.";
+      };
+
+      user = mkOption {
+        type = types.str;
+        default = "root";
+        description = "User running the ACME client.";
+      };
+
+      group = mkOption {
+        type = types.str;
+        default = "root";
+        description = "Group running the ACME client.";
+      };
+
+      postRun = mkOption {
+        type = types.lines;
+        default = "";
+        example = "systemctl reload nginx.service";
+        description = ''
+          Commands to run after certificates are re-issued. Typically
+          the web server and other servers using certificates need to
+          be reloaded.
+        '';
+      };
+
+      plugins = mkOption {
+        type = types.listOf (types.enum [
+          "cert.der" "cert.pem" "chain.der" "chain.pem" "external_pem.sh"
+          "fullchain.der" "fullchain.pem" "key.der" "key.pem" "account_key.json"
+        ]);
+        default = [ "fullchain.pem" "key.pem" "account_key.json" ];
+        description = ''
+          Plugins to enable. With default settings simp_le will
+          store public certificate bundle in <filename>fullchain.pem</filename>
+          and private key in <filename>key.pem</filename> in its state directory.
+        '';
+      };
+
+      extraDomains = mkOption {
+        type = types.attrsOf (types.nullOr types.str);
+        default = {};
+        example = {
+          "example.org" = "/srv/http/nginx";
+          "mydomain.org" = null;
+        };
+        description = ''
+          Extra domain names for which certificates are to be issued, with their
+          own server roots if needed.
+        '';
+      };
+    };
+  };
+
+in
+
+{
+
+  ###### interface
+
+  options = {
+    security.acme = {
+      directory = mkOption {
+        default = "/var/lib/acme";
+        type = types.str;
+        description = ''
+          Directory where certs and other state will be stored by default.
+        '';
+      };
+
+      validMin = mkOption {
+        type = types.int;
+        default = 30 * 24 * 3600;
+        description = "Minimum remaining validity before renewal in seconds.";
+      };
+
+      renewInterval = mkOption {
+        type = types.str;
+        default = "weekly";
+        description = ''
+          Systemd calendar expression when to check for renewal. See
+          <citerefentry><refentrytitle>systemd.time</refentrytitle>
+          <manvolnum>5</manvolnum></citerefentry>.
+        '';
+      };
+
+      certs = mkOption {
+        default = { };
+        type = types.loaOf types.optionSet;
+        description = ''
+          Attribute set of certificates to get signed and renewed.
+        '';
+        options = [ certOpts ];
+        example = {
+          "example.com" = {
+            webroot = "/var/www/challenges/";
+            email = "foo@example.com";
+            extraDomains = { "www.example.com" = null; "foo.example.com" = "/var/www/foo/"; };
+          };
+          "bar.example.com" = {
+            webroot = "/var/www/challenges/";
+            email = "bar@example.com";
+          };
+        };
+      };
+    };
+  };
+
+  ###### implementation
+  config = mkMerge [
+    (mkIf (cfg.certs != { }) {
+
+      systemd.services = flip mapAttrs' cfg.certs (cert: data:
+        let
+          cpath = "${cfg.directory}/${cert}";
+          cmdline = [ "-v" "-d" cert "--default_root" data.webroot "--valid_min" cfg.validMin ]
+                    ++ optionals (data.email != null) [ "--email" data.email ]
+                    ++ concatMap (p: [ "-f" p ]) data.plugins
+                    ++ concatLists (mapAttrsToList (name: root: [ "-d" (if root == null then name else "${name}:${root}")]) data.extraDomains);
+
+        in nameValuePair
+        ("acme-${cert}")
+        ({
+          description = "ACME cert renewal for ${cert} using simp_le";
+          after = [ "network.target" ];
+          serviceConfig = {
+            Type = "oneshot";
+            SuccessExitStatus = [ "0" "1" ];
+            PermissionsStartOnly = true;
+            User = data.user;
+            Group = data.group;
+            PrivateTmp = true;
+          };
+          path = [ pkgs.simp_le ];
+          preStart = ''
+            mkdir -p '${cfg.directory}'
+            if [ ! -d '${cpath}' ]; then
+              mkdir -m 700 '${cpath}'
+              chown '${data.user}:${data.group}' '${cpath}'
+            fi
+          '';
+          script = ''
+            cd '${cpath}'
+            set +e
+            simp_le ${concatMapStringsSep " " (arg: escapeShellArg (toString arg)) cmdline}
+            EXITCODE=$?
+            set -e
+            echo "$EXITCODE" > /tmp/lastExitCode
+            exit "$EXITCODE"
+          '';
+          postStop = ''
+            if [ -e /tmp/lastExitCode ] && [ "$(cat /tmp/lastExitCode)" = "0" ]; then
+              echo "Executing postRun hook..."
+              ${data.postRun}
+            fi
+          '';
+        })
+      );
+
+      systemd.timers = flip mapAttrs' cfg.certs (cert: data: nameValuePair
+        ("acme-${cert}")
+        ({
+          description = "timer for ACME cert renewal of ${cert}";
+          wantedBy = [ "timers.target" ];
+          timerConfig = {
+            OnCalendar = cfg.renewInterval;
+            Unit = "acme-simp_le-${cert}.service";
+          };
+        })
+      );
+    })
+
+    { meta.maintainers = with lib.maintainers; [ abbradar fpletz globin ];
+      meta.doc = ./acme.xml;
+    }
+  ];
+
+}
diff --git a/nixos/modules/security/acme.xml b/nixos/modules/security/acme.xml
new file mode 100644
index 00000000000..e32fa72c939
--- /dev/null
+++ b/nixos/modules/security/acme.xml
@@ -0,0 +1,69 @@
+<chapter xmlns="http://docbook.org/ns/docbook"
+         xmlns:xlink="http://www.w3.org/1999/xlink"
+         xmlns:xi="http://www.w3.org/2001/XInclude"
+         version="5.0"
+         xml:id="module-security-acme">
+
+<title>SSL/TLS Certificates with ACME</title>
+
+<para>NixOS supports automatic domain validation &amp; certificate
+retrieval and renewal using the ACME protocol. This is currently only
+implemented by and for Let's Encrypt. The alternative ACME client
+<literal>simp_le</literal> is used under the hood.</para>
+
+<section><title>Prerequisites</title>
+
+<para>You need to have a running HTTP server for verification. The server must
+have a webroot defined that can serve
+<filename>.well-known/acme-challenge</filename>. This directory must be
+writeable by the user that will run the ACME client.</para>
+
+<para>For instance, this generic snippet could be used for Nginx:
+
+<programlisting>
+http {
+  server {
+    server_name _;
+    listen 80;
+    listen [::]:80;
+
+    location /.well-known/acme-challenge {
+      root /var/www/challenges;
+    }
+
+    location / {
+      return 301 https://$host$request_uri;
+    }
+  }
+}
+</programlisting>
+</para>
+
+</section>
+
+<section><title>Configuring</title>
+
+<para>To enable ACME certificate retrieval &amp; renewal for a certificate for
+<literal>foo.example.com</literal>, add the following in your
+<filename>configuration.nix</filename>:
+
+<programlisting>
+security.acme.certs."foo.example.com" = {
+  webroot = "/var/www/challenges";
+  email = "foo@example.com";
+};
+</programlisting>
+</para>
+
+<para>The private key <filename>key.pem</filename> and certificate
+<filename>fullchain.pem</filename> will be put into
+<filename>/var/lib/acme/foo.example.com</filename>. The target directory can
+be configured with the option <literal>security.acme.directory</literal>.
+</para>
+
+<para>Refer to <xref linkend="ch-options" /> for all available configuration
+options for the <literal>security.acme</literal> module.</para>
+
+</section>
+
+</chapter>
diff --git a/pkgs/tools/admin/simp_le/default.nix b/pkgs/tools/admin/simp_le/default.nix
index 5f945309aac..43e361ba647 100644
--- a/pkgs/tools/admin/simp_le/default.nix
+++ b/pkgs/tools/admin/simp_le/default.nix
@@ -1,16 +1,16 @@
 { stdenv, fetchFromGitHub, pythonPackages }:
 
 pythonPackages.buildPythonPackage rec {
-  name = "simp_le-20151205";
+  name = "simp_le-20151207";
 
   src = fetchFromGitHub {
     owner = "kuba";
     repo = "simp_le";
-    rev = "976a33830759e66610970f92f6ec1a656a2c8335";
-    sha256 = "0bfa5081rmjjg9sii6pn2dskd1wh0dgrf9ic9hpisawrk0y0739i";
+    rev = "ac836bc0af988cb14dc0a83dc2039e7fa541b677";
+    sha256 = "0r07mlis81n0pmj74wjcvjpi6i3lkzs6hz8iighhk8yymn1a8rbn";
   };
 
-  propagatedBuildInputs = with pythonPackages; [ acme cryptography pytz requests2 ];
+  propagatedBuildInputs = with pythonPackages; [ acme ];
 
   meta = with stdenv.lib; {
     homepage = https://github.com/kuba/simp_le;