diff --git a/build.sh b/build.sh
index cbcd805..f6ad2e3 100755
--- a/build.sh
+++ b/build.sh
@@ -1,5 +1,6 @@
 # Build Sloth
 cargo build
+rm output.o
 FILENAME="$1"
 # Compile standard library
 ./target/debug/sloth std/extern.sloth std/stdmath.sloth std/stdio.sloth $FILENAME
diff --git a/examples/mutable.sloth b/examples/mutable.sloth
new file mode 100644
index 0000000..7ea6a96
--- /dev/null
+++ b/examples/mutable.sloth
@@ -0,0 +1,7 @@
+fn main() {
+  val test = 0;
+  println(istr(test));
+  #test = 1;
+  println(istr(test));
+  return 0;
+}
diff --git a/sloth/src/analysis/setup.rs b/sloth/src/analysis/setup.rs
index 3110f77..522d757 100644
--- a/sloth/src/analysis/setup.rs
+++ b/sloth/src/analysis/setup.rs
@@ -35,6 +35,22 @@ impl Populator {
                             name: "Float".to_owned(),
                             is_list: false,
                         }),
+                        true,
+                    )?;
+                    table.insert(identifier.to_owned(), symbol);
+                }
+                StmtKind::DefineValue {
+                    identifier, typ, ..
+                } => {
+                    // When a variable is defined add it to the symbol table of the current scope.
+                    let symbol = self.build_value_symbol(
+                        node.line(),
+                        &table,
+                        &typ.clone().unwrap_or(TypeIdentifier {
+                            name: "Float".to_owned(),
+                            is_list: false,
+                        }),
+                        false,
                     )?;
                     table.insert(identifier.to_owned(), symbol);
                 }
@@ -56,7 +72,7 @@ impl Populator {
 
                         for input in inputs {
                             let symbol =
-                                self.build_value_symbol(node.line(), &body_table, &input.typ)?;
+                                self.build_value_symbol(node.line(), &body_table, &input.typ, true)?;
                             body_table.insert(input.identifier.to_owned(), symbol);
                         }
                     }
@@ -70,6 +86,7 @@ impl Populator {
                     let symbol = Symbol::Value(ValueSymbol {
                         typ: Type::Integer,
                         id: self.reserve_id(),
+                        mutable: true,
                     });
 
                     body_table.insert(identifier.to_owned(), symbol);
@@ -90,6 +107,7 @@ impl Populator {
         line: u32,
         table: &SymbolTable,
         typ: &TypeIdentifier,
+        mutab: bool,
     ) -> Result<Symbol, AnalysisError> {
         let typ = table
             .get_type(typ)
@@ -98,6 +116,7 @@ impl Populator {
         Ok(Symbol::Value(ValueSymbol {
             typ,
             id: self.reserve_id(),
+            mutable: mutab,
         }))
     }
 
@@ -129,8 +148,10 @@ impl Populator {
             typ: Type::Function {
                 inputs,
                 output: output.into(),
+
             },
             id: self.reserve_id(),
+            mutable: true,
         }))
     }
 }
@@ -167,6 +188,9 @@ pub(super) fn propagate_types_stmt(node: &mut Stmt) -> Result<(), AnalysisError>
         StmtKind::DefineVariable { value, .. } => {
             propagate_types(value)?;
         }
+        StmtKind::DefineValue { value, .. } => {
+            propagate_types(value)?;
+        }
         StmtKind::AssignVariable { value, .. } => {
             propagate_types(value)?;
         }
diff --git a/sloth/src/codegen/mod.rs b/sloth/src/codegen/mod.rs
index 59f1ea6..7678856 100644
--- a/sloth/src/codegen/mod.rs
+++ b/sloth/src/codegen/mod.rs
@@ -233,14 +233,29 @@ impl<'ctx> Codegen<'ctx> {
                 self.builder.build_store(ptr, init_value);
                 self.references.insert(symbol.id, ptr);
             }
-            StmtKind::AssignVariable { identifier, value } => {
+            StmtKind::DefineValue {
+                identifier, value, ..
+            } => {
                 let table = code.symtable.clone();
                 let symbol = table.get_value(identifier).unwrap();
 
-                let ptr = self.references.get(&symbol.id).unwrap();
+                let ptr = self.codegen_alloca(self.type_as_basic_type(symbol.typ), identifier);
                 let init_value = self.codegen_expr(value).unwrap();
 
-                self.builder.build_store(*ptr, init_value);
+                self.builder.build_store(ptr, init_value);
+                self.references.insert(symbol.id, ptr);
+            }
+            StmtKind::AssignVariable { identifier, value } => {
+                let table = code.symtable.clone();
+                let symbol = table.get_value(identifier).unwrap();
+                if symbol.mutable {
+                    let ptr = self.references.get(&symbol.id).unwrap();
+                    let init_value = self.codegen_expr(value).unwrap();
+
+                    self.builder.build_store(*ptr, init_value);
+                } else {
+                    panic!("Val not mutable!");
+                }
             }
             StmtKind::DefineFunction(function) => {
                 let table = code.symtable.clone();
diff --git a/sloth/src/main.rs b/sloth/src/main.rs
index c181a3b..23946b2 100644
--- a/sloth/src/main.rs
+++ b/sloth/src/main.rs
@@ -100,6 +100,7 @@ fn mk_symtable() -> SymbolTable {
             output: Box::new(Type::Integer),
         },
         id: 0,
+        mutable: true,
     });
 
     let dummyf = Symbol::Value(ValueSymbol {
@@ -108,6 +109,7 @@ fn mk_symtable() -> SymbolTable {
             output: Box::new(Type::Float),
         },
         id: 0,
+        mutable: true,
     });
 
     let dummyb = Symbol::Value(ValueSymbol {
@@ -116,6 +118,7 @@ fn mk_symtable() -> SymbolTable {
             output: Box::new(Type::Boolean),
         },
         id: 0,
+        mutable: true,
     });
 
     let dummys = Symbol::Value(ValueSymbol {
@@ -124,6 +127,7 @@ fn mk_symtable() -> SymbolTable {
             output: Box::new(Type::Boolean),
         },
         id: 0,
+        mutable: true,
     });
 
     global_symtable.insert("vlen".into(), dummyi.clone());
diff --git a/sloth/src/parser/ast.rs b/sloth/src/parser/ast.rs
index 74500ef..7bc2c1b 100644
--- a/sloth/src/parser/ast.rs
+++ b/sloth/src/parser/ast.rs
@@ -195,6 +195,7 @@ impl Stmt {
                 children.push(body.as_node());
             }
             StmtKind::DefineVariable { value, .. } => children.push(value.as_node()),
+            StmtKind::DefineValue { value, .. } => children.push(value.as_node()),
             StmtKind::AssignVariable { value, .. } => children.push(value.as_node()),
             StmtKind::DefineFunction(Function { kind, .. }) => {
                 if let FunctionKind::Normal { body } = kind {
@@ -233,6 +234,11 @@ pub enum StmtKind {
         value: Expr,
         typ: Option<TypeIdentifier>,
     },
+    DefineValue {
+        identifier: String,
+        value: Expr,
+        typ: Option<TypeIdentifier>,
+    },
     AssignVariable {
         identifier: String,
         value: Expr,
diff --git a/sloth/src/parser/graph.rs b/sloth/src/parser/graph.rs
index 7b56b56..a76bf4c 100644
--- a/sloth/src/parser/graph.rs
+++ b/sloth/src/parser/graph.rs
@@ -85,6 +85,20 @@ impl GraphBuilder {
                 self.traverse_expr0(iterator)?;
                 self.traverse_stmt0(body)?;
             }
+            StmtKind::DefineValue {
+                identifier,
+                value,
+                typ,
+            } => {
+                writeln!(
+                    &mut self.graph,
+                    "N{} [shape=box label=\"DefineValue\\n\\nIdentifier={}\\lType={}\\l\"];",
+                    stmt.id,
+                    identifier,
+                    typ.clone().unwrap()
+                )?;
+                self.traverse_expr0(value)?;
+            }
             StmtKind::DefineVariable {
                 identifier,
                 value,
@@ -277,6 +291,10 @@ impl GraphBuilder {
                 writeln!(&mut self.graph, "N{} -> N{};", stmt.id, value.id)?;
                 self.traverse_expr(value)?;
             }
+            StmtKind::DefineValue { value, .. } => {
+                writeln!(&mut self.graph, "N{} -> N{};", stmt.id, value.id)?;
+                self.traverse_expr(value)?;
+            }
             StmtKind::AssignVariable { value, .. } => {
                 writeln!(&mut self.graph, "N{} -> N{};", stmt.id, value.id)?;
                 self.traverse_expr(value)?;
diff --git a/sloth/src/parser/stmt.rs b/sloth/src/parser/stmt.rs
index 75ef1b2..54534c4 100644
--- a/sloth/src/parser/stmt.rs
+++ b/sloth/src/parser/stmt.rs
@@ -16,6 +16,7 @@ impl<'a> AstParser<'a> {
             TokenType::While => self.while_stmt(),
             TokenType::For => self.for_stmt(),
             TokenType::Var => self.define_variable(),
+            TokenType::Val => self.define_value(),
             TokenType::Fn => self.define_function(false),
             TokenType::Return => self.return_stmt(),
 
@@ -149,6 +150,37 @@ impl<'a> AstParser<'a> {
         ))
     }
 
+    fn define_value(&mut self) -> Result<Stmt, ParsingError> {
+        // Consume the val token
+        self.consume(TokenType::Val, "Expected val")?;
+
+        // Get the identifier and type
+        let identifier = self.consume_identifier()?;
+        let typ = if self.consume(TokenType::Colon, "Expected ':'").is_ok() {
+            self.consume_type().ok()
+        } else {
+            None
+        };
+
+        // Get the default value
+        self.consume(TokenType::Eq, "Expected '='")?;
+        let value = self.expression()?;
+
+        self.consume(TokenType::SemiColon, "Expected ';' at end of statement")?;
+
+        let kind = StmtKind::DefineValue {
+            identifier,
+            value,
+            typ,
+        };
+
+        Ok(Stmt::new(
+            self.reserve_id(),
+            self.line,
+            kind,
+            self.top.clone(),
+        ))
+    }
     // TODO: Make argument types optional
     fn define_function(&mut self, is_foreign: bool) -> Result<Stmt, ParsingError> {
         // Consume the fn token
diff --git a/sloth/src/symtable.rs b/sloth/src/symtable.rs
index 549bb59..06c0026 100644
--- a/sloth/src/symtable.rs
+++ b/sloth/src/symtable.rs
@@ -143,6 +143,7 @@ pub enum Symbol {
 pub struct ValueSymbol {
     pub typ: Type,
     pub id: i32,
+    pub mutable: bool,
 }
 
 #[derive(Clone, Debug, PartialEq, PartialOrd)]