diff --git a/src/channels.rs b/src/channels.rs
index a671b80..5efe748 100644
--- a/src/channels.rs
+++ b/src/channels.rs
@@ -51,20 +51,22 @@ impl Member {
         }
     }
 
-    /// Highest prefix char for NAMES (`""` for a plain member).
+    /// Highest prefix char for NAMES (`""` for a plain member). The sigil per tier is
+    /// config-overridable via [`crate::modules::customprefix`].
     pub fn prefix_char(&self) -> &'static str {
+        use crate::modules::customprefix::sigil;
         if self.oprefix {
-            "!"
+            sigil(0)
         } else if self.owner {
-            "~"
+            sigil(1)
         } else if self.admin {
-            "&"
+            sigil(2)
         } else if self.op {
-            "@"
+            sigil(3)
         } else if self.halfop {
-            "%"
+            sigil(4)
         } else if self.voice {
-            "+"
+            sigil(5)
         } else {
             ""
         }
@@ -85,17 +87,18 @@ impl Member {
 
     /// Every prefix char this member holds, high→low (for the `multi-prefix` cap).
     pub fn all_prefixes(&self) -> String {
+        use crate::modules::customprefix::sigil;
         let mut s = String::new();
-        for (on, c) in [
-            (self.oprefix, '!'),
-            (self.owner, '~'),
-            (self.admin, '&'),
-            (self.op, '@'),
-            (self.halfop, '%'),
-            (self.voice, '+'),
+        for (on, i) in [
+            (self.oprefix, 0),
+            (self.owner, 1),
+            (self.admin, 2),
+            (self.op, 3),
+            (self.halfop, 4),
+            (self.voice, 5),
         ] {
             if on {
-                s.push(c);
+                s.push_str(sigil(i));
             }
         }
         s
diff --git a/src/ircd.rs b/src/ircd.rs
index 4995887..05c2a2b 100644
--- a/src/ircd.rs
+++ b/src/ircd.rs
@@ -103,6 +103,7 @@ impl Ircd {
         crate::modules::metadata::load(&mut server); // restore channel metadata
         crate::modules::reputation::load(&mut server); // restore per-IP reputation
         crate::modules::geoip::init(&mut server); // load the GeoIP database
+        crate::modules::customprefix::init(&server); // load prefix-sigil overrides
         Ircd {
             server,
             commands: command_table(),
diff --git a/src/link.rs b/src/link.rs
index 2ad2457..bc372ca 100644
--- a/src/link.rs
+++ b/src/link.rs
@@ -1434,14 +1434,8 @@ fn split_member(tok: &str) -> (String, String) {
 
 /// Map a prefix char to its mode letter (`@` → `o`, …).
 fn prefix_letter(c: char) -> char {
-    match c {
-        '~' => 'q',
-        '&' => 'a',
-        '@' => 'o',
-        '%' => 'h',
-        '+' => 'v',
-        _ => ' ',
-    }
+    // config-overridable sigils (customprefix); a linked network shares this config
+    crate::modules::customprefix::letter_for_sigil(c)
 }
 
 #[cfg(test)]
diff --git a/src/modules/customprefix.rs b/src/modules/customprefix.rs
new file mode 100644
index 0000000..928a9ae
--- /dev/null
+++ b/src/modules/customprefix.rs
@@ -0,0 +1,67 @@
+//! customprefix — override the *symbol* (sigil) of the channel prefix tiers from
+//! config, e.g. show `!` for op instead of `@`. One line per tier:
+//!
+//! ```text
+//! customprefix = op *          # ops show as *nick, PREFIX advertises it too
+//! customprefix = voice -
+//! ```
+//!
+//! Tiers: `oper founder admin op halfop voice`. Only the displayed symbol changes —
+//! the mode letters (`yqaohv`) and ranks stay fixed, so NAMES/WHO, ISUPPORT PREFIX
+//! and the S2S FJOIN burst stay consistent (a linked network must share this config,
+//! as with InspIRCd). Loaded once at boot; unset tiers keep their default sigil.
+
+use std::sync::OnceLock;
+
+use crate::server::Server;
+
+const TIER_NAMES: [&str; 6] = ["oper", "founder", "admin", "op", "halfop", "voice"];
+const LETTERS: [char; 6] = ['y', 'q', 'a', 'o', 'h', 'v'];
+const DEFAULT_SIGILS: [&str; 6] = ["!", "~", "&", "@", "%", "+"];
+
+/// The configured sigils, indexed by tier. Being a `static` its `String`s live for
+/// the program, so `sigil()` can hand out `&'static str` without leaking.
+static SIGILS: OnceLock<[String; 6]> = OnceLock::new();
+
+/// Load the `customprefix` overrides once, at boot.
+pub fn init(s: &Server) {
+    let mut a: [String; 6] = DEFAULT_SIGILS.map(String::from);
+    for line in s.conf_all("customprefix") {
+        let mut it = line.split_whitespace();
+        if let (Some(name), Some(sym)) = (it.next(), it.next()) {
+            if let Some(i) = TIER_NAMES.iter().position(|t| t.eq_ignore_ascii_case(name)) {
+                if let Some(c) = sym.chars().next() {
+                    a[i] = c.to_string();
+                }
+            }
+        }
+    }
+    let _ = SIGILS.set(a);
+}
+
+/// The sigil for tier `i` (0 = oper … 5 = voice).
+pub fn sigil(i: usize) -> &'static str {
+    SIGILS
+        .get()
+        .map(|a| a[i].as_str())
+        .unwrap_or(DEFAULT_SIGILS[i])
+}
+
+/// The prefix mode letter for a sigil char (used by the FJOIN decode); `' '` if the
+/// char isn't a prefix sigil.
+pub fn letter_for_sigil(c: char) -> char {
+    let cs = c.to_string();
+    (0..6)
+        .find(|&i| sigil(i) == cs)
+        .map(|i| LETTERS[i])
+        .unwrap_or(' ')
+}
+
+/// The ISUPPORT `PREFIX=(modes)symbols` token; `include_oper` adds the `y` tier
+/// (operprefix/ojoin).
+pub fn isupport(include_oper: bool) -> String {
+    let start = if include_oper { 0 } else { 1 };
+    let letters: String = LETTERS[start..].iter().collect();
+    let sigils: String = (start..6).map(sigil).collect();
+    format!("({letters}){sigils}")
+}
diff --git a/src/modules/mod.rs b/src/modules/mod.rs
index a617353..dc3489d 100644
--- a/src/modules/mod.rs
+++ b/src/modules/mod.rs
@@ -20,6 +20,7 @@ pub mod conn_waitpong;
 pub mod connclass;
 pub mod connectban;
 pub mod connflood;
+pub mod customprefix;
 pub mod customtitle;
 pub mod dccallow;
 pub mod denychans;
diff --git a/src/server.rs b/src/server.rs
index a0d0b93..b4874ce 100644
--- a/src/server.rs
+++ b/src/server.rs
@@ -616,12 +616,10 @@ impl Server {
         let chathist = crate::modules::chathistory::limit(self);
         let maxnick = self.conf_num("maxnick", 30usize);
         let maxchan = self.conf_num("maxchannel", 50usize);
-        // operprefix/ojoin add the server oper prefix `y` (sigil `!`) above owner
-        let prefix = if self.conf_bool("operprefix", false) || self.conf_bool("ojoin", false) {
-            "(yqaohv)!~&@%+"
-        } else {
-            "(qaohv)~&@%+"
-        };
+        // operprefix/ojoin add the server oper prefix `y` above owner; sigils are
+        // config-overridable (see modules::customprefix)
+        let include_oper = self.conf_bool("operprefix", false) || self.conf_bool("ojoin", false);
+        let prefix = crate::modules::customprefix::isupport(include_oper);
         let mut lines = vec![format!(
             "CHANTYPES=# PREFIX={prefix} CHANMODES=beIgXw,k,lfjFLHBJdK,ACDGMNOPQRSTUcimnpstuz EXTBAN=,Gbcgjmnrsy WATCH={maxwatch} MONITOR={maxmon} SILENCE={maxsil} CALLERID=g WHOX CHATHISTORY={chathist} MSGREFTYPES=timestamp,msgid UTF8ONLY CASEMAPPING=ascii NICKLEN={maxnick} CHANNELLEN={maxchan} NETWORK={}",
             self.network