diff --git a/src/urllib3/util/url.py b/src/urllib3/util/url.py
index eba42058cb..9675f74217 100644
--- a/src/urllib3/util/url.py
+++ b/src/urllib3/util/url.py
@@ -50,7 +50,7 @@
     "(?:(?:%(hex)s:){0,6}%(hex)s)?::",
 ]
 
-UNRESERVED_PAT = r"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789._!\-"
+UNRESERVED_PAT = r"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789._!\-~"
 IPV6_PAT = "(?:" + "|".join([x % _subs for x in _variations]) + ")"
 ZONE_ID_PAT = "(?:%25|%)(?:[" + UNRESERVED_PAT + "]|%[a-fA-F0-9]{2})+"
 IPV6_ADDRZ_PAT = r"\[" + IPV6_PAT + r"(?:" + ZONE_ID_PAT + r")?\]"
@@ -63,17 +63,18 @@
 BRACELESS_IPV6_ADDRZ_RE = re.compile("^" + IPV6_ADDRZ_PAT[2:-2] + "$")
 ZONE_ID_RE = re.compile("(" + ZONE_ID_PAT + r")\]$")
 
-SUBAUTHORITY_PAT = (u"^(?:(.*)@)?" u"(%s|%s|%s)" u"(?::([0-9]{0,5}))?$") % (
+SUBAUTHORITY_PAT = (u"^(?:(.*)@)?(%s|%s|%s)(?::([0-9]{0,5}))?$") % (
     REG_NAME_PAT,
     IPV4_PAT,
     IPV6_ADDRZ_PAT,
 )
 SUBAUTHORITY_RE = re.compile(SUBAUTHORITY_PAT, re.UNICODE | re.DOTALL)
 
-ZONE_ID_CHARS = set(
-    "ABCDEFGHIJKLMNOPQRSTUVWXYZ" "abcdefghijklmnopqrstuvwxyz" "0123456789._!-"
+UNRESERVED_CHARS = set(
+    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789._-~"
 )
-USERINFO_CHARS = ZONE_ID_CHARS | set("$&'()*+,;=:")
+SUB_DELIM_CHARS = set("!$&'()*+,;=")
+USERINFO_CHARS = UNRESERVED_CHARS | SUB_DELIM_CHARS | {":"}
 PATH_CHARS = USERINFO_CHARS | {"@", "/"}
 QUERY_CHARS = FRAGMENT_CHARS = PATH_CHARS | {"?"}
 
@@ -290,7 +291,7 @@ def _normalize_host(host, scheme):
                         zone_id = zone_id[3:]
                     else:
                         zone_id = zone_id[1:]
-                    zone_id = "%" + _encode_invalid_chars(zone_id, ZONE_ID_CHARS)
+                    zone_id = "%" + _encode_invalid_chars(zone_id, UNRESERVED_CHARS)
                     return host[:start].lower() + zone_id + host[end:]
                 else:
                     return host.lower()
diff --git a/test/test_util.py b/test/test_util.py
index 73fad715c0..42c388243d 100644
--- a/test/test_util.py
+++ b/test/test_util.py
@@ -170,6 +170,10 @@ def test_invalid_url(self, url):
         "url, expected_normalized_url",
         [
             ("HTTP://GOOGLE.COM/MAIL/", "http://google.com/MAIL/"),
+            (
+                "http://user@domain.com:password@example.com/~tilde@?@",
+                "http://user%40domain.com:password@example.com/~tilde@?@",
+            ),
             (
                 "HTTP://JeremyCline:Hunter2@Example.com:8080/",
                 "http://JeremyCline:Hunter2@example.com:8080/",