diff --git a/doc/src/sgml/ref/psql-ref.sgml b/doc/src/sgml/ref/psql-ref.sgml
index 1f29615f833863f3dec9080caa1dfcc982cc98c6..62a3b21209d60b43c6b4e5ed9ee07044ea301962 100644
--- a/doc/src/sgml/ref/psql-ref.sgml
+++ b/doc/src/sgml/ref/psql-ref.sgml
@@ -796,23 +796,31 @@ testdb=>
       </varlistentry>
 
       <varlistentry>
-        <term><literal>\c</literal> or <literal>\connect</literal> <literal>[ <replaceable class="parameter">dbname</replaceable> [ <replaceable class="parameter">username</replaceable> ] [ <replaceable class="parameter">host</replaceable> ] [ <replaceable class="parameter">port</replaceable> ] ]</literal></term>
+        <term><literal>\c</literal> or <literal>\connect</literal> <literal>[ <replaceable class="parameter">dbname</replaceable> [ <replaceable class="parameter">username</replaceable> ] [ <replaceable class="parameter">host</replaceable> ] [ <replaceable class="parameter">port</replaceable> ] ] | <replaceable class="parameter">conninfo</replaceable> </literal></term>
         <listitem>
         <para>
         Establishes a new connection to a <productname>PostgreSQL</>
-        server. If the new connection is successfully made, the
-        previous connection is closed. If any of <replaceable
-        class="parameter">dbname</replaceable>, <replaceable
-        class="parameter">username</replaceable>, <replaceable
-        class="parameter">host</replaceable> or <replaceable
-        class="parameter">port</replaceable> are omitted or specified
-        as <literal>-</literal>, the value of that parameter from the
-        previous connection is used. If there is no previous
-        connection, the <application>libpq</application> default for
-        the parameter's value is used.
+        server.  The connection parameters to use can be specified either
+        using a positional syntax, or using <literal>conninfo</> connection
+        strings as detailed in <xref linkend="libpq-connstring">.
         </para>
 
         <para>
+        When using positional parameters, if any of
+        <replaceable class="parameter">dbname</replaceable>,
+        <replaceable class="parameter">username</replaceable>,
+        <replaceable class="parameter">host</replaceable> or
+        <replaceable class="parameter">port</replaceable> are omitted or
+        specified as <literal>-</literal>, the value of that parameter from
+        the previous connection is used; if there is no previous connection,
+        the <application>libpq</application> default for the parameter's value
+        is used.  When using <literal>conninfo</> strings, no values from the
+        previous connection are used for the new connection.
+        </para>
+
+        <para>
+        If the new connection is successfully made, the previous
+        connection is closed.
         If the connection attempt failed (wrong user name, access
         denied, etc.), the previous connection will only be kept if
         <application>psql</application> is in interactive mode. When
@@ -822,6 +830,16 @@ testdb=&gt;
         mechanism that scripts are not accidentally acting on the
         wrong database on the other hand.
         </para>
+
+        <para>
+        Examples:
+        </para>
+<programlisting>
+=&gt; \c mydb myuser host.dom 6432
+=&gt; \c service=foo
+=&gt; \c "host=localhost port=5432 dbname=mydb connect_timeout=10 sslmode=disable"
+=&gt; \c postgresql://tom@localhost/mydb?application_name=myapp
+</programlisting>
         </listitem>
       </varlistentry>
 
diff --git a/src/bin/psql/command.c b/src/bin/psql/command.c
index 916f1c6301ebaeed30faf26af08e9dcce90351e0..70b7d3be151e10731d6903b2e1cc29d9ea55ba94 100644
--- a/src/bin/psql/command.c
+++ b/src/bin/psql/command.c
@@ -1608,6 +1608,8 @@ do_connect(char *dbname, char *user, char *host, char *port)
 	PGconn	   *o_conn = pset.db,
 			   *n_conn;
 	char	   *password = NULL;
+	bool		keep_password;
+	bool		has_connection_string;
 
 	if (!o_conn && (!dbname || !user || !host || !port))
 	{
@@ -1621,8 +1623,7 @@ do_connect(char *dbname, char *user, char *host, char *port)
 		return false;
 	}
 
-	if (!dbname)
-		dbname = PQdb(o_conn);
+	/* grab values from the old connection, unless supplied by caller */
 	if (!user)
 		user = PQuser(o_conn);
 	if (!host)
@@ -1630,6 +1631,27 @@ do_connect(char *dbname, char *user, char *host, char *port)
 	if (!port)
 		port = PQport(o_conn);
 
+	has_connection_string =
+		dbname ? recognized_connection_string(dbname) : false;
+
+	/*
+	 * Any change in the parameters read above makes us discard the password.
+	 * We also discard it if we're to use a conninfo rather than the positional
+	 * syntax.
+	 */
+	keep_password =
+		((strcmp(user, PQuser(o_conn)) == 0) &&
+		 (!host || strcmp(host, PQhost(o_conn)) == 0) &&
+		 (strcmp(port, PQport(o_conn)) == 0) &&
+		 !has_connection_string);
+
+	/*
+	 * Grab dbname from old connection unless supplied by caller.  No password
+	 * discard if this changes: passwords aren't (usually) database-specific.
+	 */
+	if (!dbname)
+		dbname = PQdb(o_conn);
+
 	/*
 	 * If the user asked to be prompted for a password, ask for one now. If
 	 * not, use the password from the old connection, provided the username
@@ -1644,9 +1666,13 @@ do_connect(char *dbname, char *user, char *host, char *port)
 	{
 		password = prompt_for_password(user);
 	}
-	else if (o_conn && user && strcmp(PQuser(o_conn), user) == 0)
+	else if (o_conn && keep_password)
 	{
-		password = pg_strdup(PQpass(o_conn));
+		password = PQpass(o_conn);
+		if (password && *password)
+			password = pg_strdup(password);
+		else
+			password = NULL;
 	}
 
 	while (true)
@@ -1654,32 +1680,39 @@ do_connect(char *dbname, char *user, char *host, char *port)
 #define PARAMS_ARRAY_SIZE	8
 		const char **keywords = pg_malloc(PARAMS_ARRAY_SIZE * sizeof(*keywords));
 		const char **values = pg_malloc(PARAMS_ARRAY_SIZE * sizeof(*values));
+		int			paramnum = 0;
+
+		keywords[0] = "dbname";
+		values[0] = dbname;
+
+		if (!has_connection_string)
+		{
+			keywords[++paramnum] = "host";
+			values[paramnum] = host;
+			keywords[++paramnum] = "port";
+			values[paramnum] = port;
+			keywords[++paramnum] = "user";
+			values[paramnum] = user;
+		}
+		keywords[++paramnum] = "password";
+		values[paramnum] = password;
+		keywords[++paramnum] = "fallback_application_name";
+		values[paramnum] = pset.progname;
+		keywords[++paramnum] = "client_encoding";
+		values[paramnum] = (pset.notty || getenv("PGCLIENTENCODING")) ? NULL : "auto";
 
-		keywords[0] = "host";
-		values[0] = host;
-		keywords[1] = "port";
-		values[1] = port;
-		keywords[2] = "user";
-		values[2] = user;
-		keywords[3] = "password";
-		values[3] = password;
-		keywords[4] = "dbname";
-		values[4] = dbname;
-		keywords[5] = "fallback_application_name";
-		values[5] = pset.progname;
-		keywords[6] = "client_encoding";
-		values[6] = (pset.notty || getenv("PGCLIENTENCODING")) ? NULL : "auto";
-		keywords[7] = NULL;
-		values[7] = NULL;
+		/* add array terminator */
+		keywords[++paramnum] = NULL;
+		values[paramnum] = NULL;
 
 		n_conn = PQconnectdbParams(keywords, values, true);
 
-		free(keywords);
-		free(values);
+		pg_free(keywords);
+		pg_free(values);
 
 		/* We can immediately discard the password -- no longer needed */
 		if (password)
-			free(password);
+			pg_free(password);
 
 		if (PQstatus(n_conn) == CONNECTION_OK)
 			break;
diff --git a/src/bin/psql/common.c b/src/bin/psql/common.c
index 2e7d9a45cb388de2efb8429cf0b593f11f187d68..ff01368531a313f97834cf6413561b060d2f7d56 100644
--- a/src/bin/psql/common.c
+++ b/src/bin/psql/common.c
@@ -1846,3 +1846,44 @@ expand_tilde(char **filename)
 
 	return;
 }
+
+/*
+ * Checks if connection string starts with either of the valid URI prefix
+ * designators.
+ *
+ * Returns the URI prefix length, 0 if the string doesn't contain a URI prefix.
+ *
+ * XXX This is a duplicate of the eponymous libpq function.
+ */
+static int
+uri_prefix_length(const char *connstr)
+{
+	/* The connection URI must start with either of the following designators: */
+	static const char uri_designator[] = "postgresql://";
+	static const char short_uri_designator[] = "postgres://";
+
+	if (strncmp(connstr, uri_designator,
+				sizeof(uri_designator) - 1) == 0)
+		return sizeof(uri_designator) - 1;
+
+	if (strncmp(connstr, short_uri_designator,
+				sizeof(short_uri_designator) - 1) == 0)
+		return sizeof(short_uri_designator) - 1;
+
+	return 0;
+}
+
+/*
+ * Recognized connection string either starts with a valid URI prefix or
+ * contains a "=" in it.
+ *
+ * Must be consistent with parse_connection_string: anything for which this
+ * returns true should at least look like it's parseable by that routine.
+ *
+ * XXX This is a duplicate of the eponymous libpq function.
+ */
+bool
+recognized_connection_string(const char *connstr)
+{
+	return uri_prefix_length(connstr) != 0 || strchr(connstr, '=') != NULL;
+}
diff --git a/src/bin/psql/common.h b/src/bin/psql/common.h
index cdb0187feb2b3bf1d58a953317c65967dec000d8..3c3ffa3f1410d1667cab54c0fafc3efaa22ba44e 100644
--- a/src/bin/psql/common.h
+++ b/src/bin/psql/common.h
@@ -46,4 +46,6 @@ extern const char *session_username(void);
 
 extern void expand_tilde(char **filename);
 
+extern bool recognized_connection_string(const char *connstr);
+
 #endif   /* COMMON_H */
diff --git a/src/bin/psql/help.c b/src/bin/psql/help.c
index f58f5e52f3303d42fa91ffa7c25b9d4e458cb99f..ea05c3e37be9d68cd668c91cbbe39d8762bada3f 100644
--- a/src/bin/psql/help.c
+++ b/src/bin/psql/help.c
@@ -260,11 +260,11 @@ slashUsage(unsigned short int pager)
 
 	fprintf(output, _("Connection\n"));
 	if (currdb)
-		fprintf(output, _("  \\c[onnect] [DBNAME|- USER|- HOST|- PORT|-]\n"
+		fprintf(output, _("  \\c[onnect] {[DBNAME|- USER|- HOST|- PORT|-] | conninfo}\n"
 						  "                         connect to new database (currently \"%s\")\n"),
 				currdb);
 	else
-		fprintf(output, _("  \\c[onnect] [DBNAME|- USER|- HOST|- PORT|-]\n"
+		fprintf(output, _("  \\c[onnect] {[DBNAME|- USER|- HOST|- PORT|-] | conninfo}\n"
 						  "                         connect to new database (currently no connection)\n"));
 	fprintf(output, _("  \\encoding [ENCODING]   show or set client encoding\n"));
 	fprintf(output, _("  \\password [USERNAME]   securely change the password for a user\n"));
diff --git a/src/bin/psql/tab-complete.c b/src/bin/psql/tab-complete.c
index dfcb66ba6dea54e909f82dd6aad619c8b0eb41c2..5a4fd5c87315282cf2ca993df4d62c10c24b96ba 100644
--- a/src/bin/psql/tab-complete.c
+++ b/src/bin/psql/tab-complete.c
@@ -3707,10 +3707,15 @@ psql_completion(const char *text, int start, int end)
 		COMPLETE_WITH_LIST_CS(my_list);
 	}
 	else if (strcmp(prev_wd, "\\connect") == 0 || strcmp(prev_wd, "\\c") == 0)
-		COMPLETE_WITH_QUERY(Query_for_list_of_databases);
+	{
+		if (!recognized_connection_string(text))
+			COMPLETE_WITH_QUERY(Query_for_list_of_databases);
+	}
 	else if (strcmp(prev2_wd, "\\connect") == 0 || strcmp(prev2_wd, "\\c") == 0)
-		COMPLETE_WITH_QUERY(Query_for_list_of_roles);
-
+	{
+		if (!recognized_connection_string(prev_wd))
+			COMPLETE_WITH_QUERY(Query_for_list_of_roles);
+	}
 	else if (strncmp(prev_wd, "\\da", strlen("\\da")) == 0)
 		COMPLETE_WITH_SCHEMA_QUERY(Query_for_list_of_aggregates, NULL);
 	else if (strncmp(prev_wd, "\\db", strlen("\\db")) == 0)
diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index e2a06b3d929c947d0322d40aeb09948eef59042f..fa8a33f40a713e3b0c2de544a5658efba126f8f5 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -4197,6 +4197,8 @@ parse_connection_string(const char *connstr, PQExpBuffer errorMessage,
  * designators.
  *
  * Returns the URI prefix length, 0 if the string doesn't contain a URI prefix.
+ *
+ * XXX this is duplicated in psql/common.c.
  */
 static int
 uri_prefix_length(const char *connstr)
@@ -4218,6 +4220,8 @@ uri_prefix_length(const char *connstr)
  *
  * Must be consistent with parse_connection_string: anything for which this
  * returns true should at least look like it's parseable by that routine.
+ *
+ * XXX this is duplicated in psql/common.c
  */
 static bool
 recognized_connection_string(const char *connstr)