diff --git a/src/or/config.c b/src/or/config.c
index 64c9796792..2f5ba6c6f7 100644
--- a/src/or/config.c
+++ b/src/or/config.c
@@ -636,6 +636,7 @@ STATIC config_format_t options_format = {
   OR_OPTIONS_MAGIC,
   STRUCT_OFFSET(or_options_t, magic_),
   option_abbrevs_,
+  NULL,
   option_vars_,
   options_validate_cb,
   NULL
diff --git a/src/or/confparse.c b/src/or/confparse.c
index 3532b39d93..233cc7c77d 100644
--- a/src/or/confparse.c
+++ b/src/or/confparse.c
@@ -181,6 +181,26 @@ config_free_lines(config_line_t *front)
   }
 }
 
+/** If <b>key</b> is a deprecated configuration option, return the message
+ * explaining why it is deprecated (which may be an empty string). Return NULL
+ * if it is not deprecated. The <b>key</b> field must be fully expanded. */
+static const char *
+config_find_deprecation(const config_format_t *fmt, const char *key)
+{
+  if (BUG(fmt == NULL) || BUG(key == NULL))
+    return NULL;
+  if (fmt->deprecations == NULL)
+    return NULL;
+
+  config_deprecation_t *d;
+  for (d = fmt->deprecations; d->name; ++d) {
+    if (!strcasecmp(d->name, key)) {
+      return d->why_deprecated ? d->why_deprecated : "";
+    }
+  }
+  return NULL;
+}
+
 /** As config_find_option, but return a non-const pointer. */
 config_var_t *
 config_find_option_mutable(config_format_t *fmt, const char *key)
@@ -463,6 +483,15 @@ config_mark_lists_fragile(const config_format_t *fmt, void *options)
   }
 }
 
+void
+warn_deprecated_option(const char *what, const char *why)
+{
+  log_warn(LD_CONFIG, "The %s option is deprecated, and will most likely "
+           "be removed in a future version of Tor.%s (If you think this is "
+           "a mistake, please let us know!)",
+           what, why);
+}
+
 /** If <b>c</b> is a syntactically valid configuration line, update
  * <b>options</b> with its value and return 0.  Otherwise return -1 for bad
  * key, -2 for bad value.
@@ -502,6 +531,11 @@ config_assign_line(const config_format_t *fmt, void *options,
     c->key = tor_strdup(var->name);
   }
 
+  const char *deprecation_msg = config_find_deprecation(fmt, var->name);
+  if (deprecation_msg) {
+    warn_deprecated_option(var->name, deprecation_msg);
+  }
+
   if (!strlen(c->value)) {
     /* reset or clear it, then return */
     if (!clear_first) {
diff --git a/src/or/confparse.h b/src/or/confparse.h
index ca6fb5ec43..415d680d2e 100644
--- a/src/or/confparse.h
+++ b/src/or/confparse.h
@@ -48,6 +48,11 @@ typedef struct config_abbrev_t {
   int warn;
 } config_abbrev_t;
 
+typedef struct config_deprecation_t {
+  const char *name;
+  const char *why_deprecated;
+} config_deprecation_t;
+
 /* Handy macro for declaring "In the config file or on the command line,
  * you can abbreviate <b>tok</b>s as <b>tok</b>". */
 #define PLURAL(tok) { #tok, #tok "s", 0, 0 }
@@ -76,6 +81,7 @@ typedef struct config_format_t {
   off_t magic_offset; /**< Offset of the magic value within the struct. */
   config_abbrev_t *abbrevs; /**< List of abbreviations that we expand when
                              * parsing this format. */
+  config_deprecation_t *deprecations; /** List of deprecated options */
   config_var_t *vars; /**< List of variables we recognize, their default
                        * values, and where we stick them in the structure. */
   validate_fn_t validate_fn; /**< Function to validate config. */
@@ -125,6 +131,8 @@ void config_free_lines(config_line_t *front);
 const char *config_expand_abbrev(const config_format_t *fmt,
                                  const char *option,
                                  int command_line, int warn_obsolete);
+void warn_deprecated_option(const char *what, const char *why);
+
 
 #endif
 
diff --git a/src/or/shared_random_state.c b/src/or/shared_random_state.c
index 52a0034db7..c344a45b7c 100644
--- a/src/or/shared_random_state.c
+++ b/src/or/shared_random_state.c
@@ -86,6 +86,7 @@ static const config_format_t state_format = {
   SR_DISK_STATE_MAGIC,
   STRUCT_OFFSET(sr_disk_state_t, magic_),
   NULL,
+  NULL,
   state_vars,
   disk_state_validate_cb,
   &state_extra_var,
diff --git a/src/or/statefile.c b/src/or/statefile.c
index 9594d9cec3..c2f31d69e5 100644
--- a/src/or/statefile.c
+++ b/src/or/statefile.c
@@ -121,6 +121,7 @@ static const config_format_t state_format = {
   OR_STATE_MAGIC,
   STRUCT_OFFSET(or_state_t, magic_),
   state_abbrevs_,
+  NULL,
   state_vars_,
   or_state_validate_cb,
   &state_extra_var,