diff --git a/Cargo.lock b/Cargo.lock
index d3b6965..6380ee8 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -3,3 +3,55 @@
 [[package]]
 name = "adduser"
 version = "0.1.0"
+dependencies = [
+ "lazy_static",
+ "regex",
+]
+
+[[package]]
+name = "aho-corasick"
+version = "0.7.13"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "043164d8ba5c4c3035fec9bbee8647c0261d788f3474306f93bb65901cae0e86"
+dependencies = [
+ "memchr",
+]
+
+[[package]]
+name = "lazy_static"
+version = "1.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e2abad23fbc42b3700f2f279844dc832adb2b2eb069b2df918f455c4e18cc646"
+
+[[package]]
+name = "memchr"
+version = "2.3.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3728d817d99e5ac407411fa471ff9800a778d88a24685968b36824eaf4bee400"
+
+[[package]]
+name = "regex"
+version = "1.3.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9c3780fcf44b193bc4d09f36d2a3c87b251da4a046c87795a0d35f4f927ad8e6"
+dependencies = [
+ "aho-corasick",
+ "memchr",
+ "regex-syntax",
+ "thread_local",
+]
+
+[[package]]
+name = "regex-syntax"
+version = "0.6.18"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "26412eb97c6b088a6997e05f69403a802a92d520de2f8e63c2b65f9e0f47c4e8"
+
+[[package]]
+name = "thread_local"
+version = "1.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d40c6d1b69745a6ec6fb1ca717914848da4b44ae29d9b3080cbee91d72a69b14"
+dependencies = [
+ "lazy_static",
+]
diff --git a/Cargo.toml b/Cargo.toml
index 4882398..4188fd3 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -7,3 +7,5 @@ edition = "2018"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+regex = "1"
+lazy_static = "1.4"
diff --git a/src/lib.rs b/src/lib.rs
index bf8894b..e942693 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,3 +1,6 @@
+#[macro_use]
+extern crate lazy_static;
+
 pub mod passwd;
 pub mod userlib_error;
 pub use passwd::{Password, Username};
diff --git a/src/passwd.rs b/src/passwd.rs
index 8f8f372..09742bd 100644
--- a/src/passwd.rs
+++ b/src/passwd.rs
@@ -7,6 +7,8 @@
 )]
 #![allow(clippy::non_ascii_literal)]
 
+use regex::Regex;
+
 use crate::userlib_error::UserLibError;
 use std::cmp::Eq;
 use std::convert::TryFrom;
@@ -259,7 +261,15 @@ impl Display for Username<'_> {
 impl<'a> TryFrom<&'a str> for Username<'a> {
     type Error = UserLibError;
     fn try_from(source: &'a str) -> std::result::Result<Self, Self::Error> {
-        Ok(Self { username: source })
+        lazy_static! {
+            static ref USERVALIDATION: Regex =
+                Regex::new("^[a-z_]([a-z0-9_-]{0,31}|[a-z0-9_-]{0,30}\\$)$").unwrap();
+        }
+        if USERVALIDATION.is_match(source) {
+            Ok(Self { username: source })
+        } else {
+            Err(UserLibError::Message("Invalid username".into()))
+        }
     }
 }
 
@@ -386,6 +396,37 @@ impl<'a> TryFrom<&'a str> for ShellPath<'a> {
 
 // Tests ----------------------------------------------------------------------
 
+#[test]
+fn test_username_validation() {
+    // Failing tests
+    let umlauts = Username::try_from("täst"); // umlauts
+    assert_eq!(
+        Err(UserLibError::Message("Invalid username".into())),
+        umlauts
+    );
+    let number_first = Username::try_from("11elf"); // numbers first
+    assert_eq!(
+        Err(UserLibError::Message("Invalid username".into())),
+        number_first
+    );
+    let slashes = Username::try_from("test/name"); // slashes in the name
+    assert_eq!(
+        Err(UserLibError::Message("Invalid username".into())),
+        slashes
+    );
+    let long = Username::try_from("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"); // maximum size 32 letters
+    assert_eq!(Err(UserLibError::Message("Invalid username".into())), long);
+    // Working tests
+    let single = Username::try_from("t"); // single characters are ok
+    assert_eq!(single.unwrap().username, "t");
+    let normal = Username::try_from("superman"); // regular username
+    assert_eq!(normal.unwrap().username, "superman");
+    let normal = Username::try_from("anna3pete"); // regular username containing a number
+    assert_eq!(normal.unwrap().username, "anna3pete");
+    let normal = Username::try_from("enya$"); // regular username ending in a $
+    assert_eq!(normal.unwrap().username, "enya$");
+}
+
 #[test]
 fn test_default_user() {
     // Check if a user can be created.