diff --git a/crates/ide-core/src/proxy_settings.rs b/crates/ide-core/src/proxy_settings.rs
index 564c2df90..ebae548d7 100644
--- a/crates/ide-core/src/proxy_settings.rs
+++ b/crates/ide-core/src/proxy_settings.rs
@@ -207,6 +207,58 @@ impl ProxySettings {
         env.push((OsString::from("no_proxy"), Some(OsString::from(no_proxy))));
         env
     }
+
+    /// System properties that make a JVM follow this configuration. A JVM reads none of
+    /// [`Self::child_env`]: a Java tool (jetty, Maven's resolver, a language server's own
+    /// HTTP client) goes direct without these, and a repository its proxy answers in
+    /// milliseconds can then hang it instead.
+    pub fn jvm_args(&self) -> Vec<String> {
+        match self.mode {
+            // macOS and Windows JVMs read the system proxy with this one.
+            ProxyMode::Auto => vec!["-Djava.net.useSystemProxies=true".into()],
+            ProxyMode::None => Vec::new(),
+            ProxyMode::Manual if self.manual() => self.manual_jvm_args(),
+            ProxyMode::Manual => Vec::new(),
+        }
+    }
+
+    fn manual_jvm_args(&self) -> Vec<String> {
+        let (host, port) = (self.host.trim(), self.port);
+        match self.kind {
+            ProxyKind::Http => {
+                // HTTPS hosts read `https.proxyHost`, plain ones `http.proxyHost`.
+                let mut args = vec![
+                    format!("-Dhttp.proxyHost={host}"),
+                    format!("-Dhttp.proxyPort={port}"),
+                    format!("-Dhttps.proxyHost={host}"),
+                    format!("-Dhttps.proxyPort={port}"),
+                ];
+                let hosts = self.non_proxy_hosts();
+                if !hosts.is_empty() {
+                    args.push(format!("-Dhttp.nonProxyHosts={}", hosts.join("|")));
+                }
+                args
+            }
+            // SOCKS proxies every TCP connection, so there is one property pair.
+            ProxyKind::Socks => vec![
+                format!("-DsocksProxyHost={host}"),
+                format!("-DsocksProxyPort={port}"),
+                "-Djava.net.useSystemProxies=false".into(),
+            ],
+        }
+    }
+
+    /// [`Self::no_proxy`] in the JVM's `http.nonProxyHosts` format: `|` between host
+    /// globs. CIDR ranges and IPv6 literals have no equivalent there and are dropped.
+    fn non_proxy_hosts(&self) -> Vec<String> {
+        let mut hosts: Vec<String> = LOOPBACK.iter().filter(|h| !h.contains(':')).map(|h| (*h).to_owned()).collect();
+        for entry in self.no_proxy_entries() {
+            if !entry.contains(['/', ':', '[', ']']) && !hosts.contains(&entry) {
+                hosts.push(entry);
+            }
+        }
+        hosts
+    }
 }
 
 /// Case-insensitive host glob (`pattern` is lowercase): `*` matches any run of characters.
@@ -292,6 +344,34 @@ mod tests {
         assert!(p.child_env().is_empty());
     }
 
+    #[test]
+    fn jvm_args_carry_the_proxy_as_system_properties() {
+        // A JVM reads none of `child_env`: a Java language server needs these to not go
+        // direct while curl, git and Node follow the environment.
+        assert_eq!(ProxySettings::default().jvm_args(), ["-Djava.net.useSystemProxies=true"]);
+        assert!(ProxySettings { mode: ProxyMode::None, ..manual("proxy", 3128) }.jvm_args().is_empty());
+        assert_eq!(
+            manual("proxy.corp", 3128).jvm_args(),
+            [
+                "-Dhttp.proxyHost=proxy.corp",
+                "-Dhttp.proxyPort=3128",
+                "-Dhttps.proxyHost=proxy.corp",
+                "-Dhttps.proxyPort=3128",
+                "-Dhttp.nonProxyHosts=localhost|127.0.0.1",
+            ]
+        );
+        let socks = ProxySettings { kind: ProxyKind::Socks, ..manual("10.0.0.1", 1080) };
+        assert_eq!(socks.jvm_args()[..2], ["-DsocksProxyHost=10.0.0.1", "-DsocksProxyPort=1080"]);
+        // `http.nonProxyHosts` takes host globs: CIDR ranges and IPv6 literals drop out.
+        let p = ProxySettings {
+            no_proxy: "*.corp.com, 172.0.0.0/8, [::1], ::1, localhost".into(),
+            ..manual("proxy.corp", 3128)
+        };
+        assert_eq!(p.jvm_args().last().unwrap(), "-Dhttp.nonProxyHosts=localhost|127.0.0.1|*.corp.com");
+        // A manual proxy without a host connects directly, and so does its JVM.
+        assert!(manual(" ", 80).jvm_args().is_empty());
+    }
+
     #[test]
     fn manual_http_and_socks_urls() {
         let p = manual("proxy.corp", 3128);
diff --git a/crates/ide-sdk/src/java.rs b/crates/ide-sdk/src/java.rs
index 9d104583a..21b217dc0 100644
--- a/crates/ide-sdk/src/java.rs
+++ b/crates/ide-sdk/src/java.rs
@@ -313,6 +313,19 @@ fn text_key(text: &str) -> String {
     format!("{h:016x}")
 }
 
+fn add_jdtls_proxy_args(args: &mut Vec<String>, proxy: &ide_core::proxy_settings::ProxySettings) {
+    for arg in proxy.jvm_args() {
+        let key = arg.split('=').next().unwrap_or(arg.as_str());
+        if !args.iter().enumerate().any(|(i, a)| {
+            let value =
+                a.strip_prefix("--jvm-arg=").or_else(|| (i > 0 && args[i - 1] == "--jvm-arg").then_some(a.as_str()));
+            value.is_some_and(|a| a.split('=').next() == Some(key))
+        }) {
+            args.push(format!("--jvm-arg={arg}"));
+        }
+    }
+}
+
 const METADATA_PROPERTY: &str = "java.import.generatesMetadataFilesAtProjectRoot";
 
 /// jdtls: its Eclipse workspace (`-data`) lives under the IDE's data
@@ -367,6 +380,10 @@ pub fn configure_jdtls(
         cfg.args.push(format!("--jvm-arg=-javaagent:{}", jar.to_string_lossy()));
     }
     crate::jdtls::add_default_vm_args(&mut cfg.args);
+    // jdtls resolves Maven dependencies through its own HTTP client, and a JVM reads none
+    // of the `HTTP_PROXY` / `HTTPS_PROXY` it inherits: pass the same proxy as system
+    // properties. One the user set in their own JVM arguments wins.
+    add_jdtls_proxy_args(&mut cfg.args, &ide_core::proxy_settings::proxy());
     let managed = language_server_runtimes_dir(data_dir);
     let managed = dunce::canonicalize(&managed).unwrap_or(managed);
     let project_jdks: Vec<_> = project_jdk
@@ -705,6 +722,35 @@ mod tests {
         assert!(other.args.is_empty() && other.initialization_options.is_none());
     }
 
+    #[test]
+    fn jdtls_proxy_properties_respect_exact_user_overrides() {
+        use ide_core::proxy_settings::{ProxyMode, ProxySettings};
+        let proxy =
+            ProxySettings { mode: ProxyMode::Manual, host: "ide.proxy".into(), port: 3128, ..Default::default() };
+        for (user_arg, overridden) in [
+            ("--jvm-arg=-Dhttp.proxyHost=user.proxy", true),
+            ("--jvm-arg=-Dhttp.proxyHost", true),
+            ("--jvm-arg=-Dhttp.proxyHostSuffix=unrelated", false),
+            ("--jvm-arg=-Dother=-Dhttp.proxyHost", false),
+            ("/workspace/-Dhttp.proxyHost", false),
+        ] {
+            let mut forms = vec![vec![user_arg.to_owned()]];
+            if let Some(value) = user_arg.strip_prefix("--jvm-arg=") {
+                forms.push(vec!["--jvm-arg".into(), value.into()]);
+            }
+            for mut args in forms {
+                let user_args = args.clone();
+                add_jdtls_proxy_args(&mut args, &proxy);
+                assert_eq!(args[..user_args.len()], user_args);
+                assert_eq!(args.contains(&"--jvm-arg=-Dhttp.proxyHost=ide.proxy".into()), !overridden, "{user_arg}");
+                assert!(args.contains(&"--jvm-arg=-Dhttps.proxyHost=ide.proxy".into()));
+                let before = args.clone();
+                add_jdtls_proxy_args(&mut args, &proxy);
+                assert_eq!(args, before, "idempotent: {user_arg}");
+            }
+        }
+    }
+
     #[test]
     fn jdtls_lombok_agent() {
         let jdtls = || -> LanguageServerConfig { toml::from_str("name = \"jdtls\"\ncommand = \"jdtls\"").unwrap() };