diff --git a/CHANGELOG.md b/CHANGELOG.md
index bc251d7..d9926f6 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,7 @@
 - Multiple listen addresses for HTTP-01 and TLS-ALPN-01 solvers (`listen = ["[::]:80", "[::]:8080"]`). Certforge tries all addresses and succeeds if at least one binds. Useful for initial provisioning when a proxy isn't running yet.
 - `dane-check` now queries published TLSA records from DNS and verifies them against expected values. Exits with code 1 if any records are missing or mismatched.
 - Configurable DNS propagation delay per solver (`propagation_delay`, default 5s).
+- Implement `account deactivate` command.
 
 ### Fixes
 
diff --git a/src/acme.rs b/src/acme.rs
index 3ff4328..e173e56 100644
--- a/src/acme.rs
+++ b/src/acme.rs
@@ -254,4 +254,9 @@ impl AcmeClient {
     pub fn account(&self) -> &Account {
         &self.account
     }
+
+    pub async fn deactivate(self) -> Result<()> {
+        self.account.deactivate().await?;
+        Ok(())
+    }
 }
diff --git a/src/main.rs b/src/main.rs
index 303c3bb..6b5e147 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -90,7 +90,25 @@ async fn main() -> anyhow::Result<()> {
                     println!("Account ID: {}", client.account().id());
                 }
                 AccountAction::Deactivate => {
-                    tracing::warn!("account deactivation not yet implemented");
+                    let client = acme::AcmeClient::load(&config.acme).await?;
+                    let id = client.account().id().to_string();
+                    client.deactivate().await?;
+
+                    // Remove local credentials so show/renew don't use the stale account
+                    if let Some(path) = &config.acme.account_key_credential
+                        && path.exists()
+                    {
+                        std::fs::remove_file(path)?;
+                        tracing::info!(path = %path.display(), "removed account credential");
+                    }
+                    if let Some(path) = &config.acme.account_key_path
+                        && path.exists()
+                    {
+                        std::fs::remove_file(path)?;
+                        tracing::info!(path = %path.display(), "removed account key file");
+                    }
+
+                    println!("Account {id} deactivated");
                 }
             }
         }