diff --git a/valuescript_common/src/instruction_byte.rs b/valuescript_common/src/instruction_byte.rs
index 48138a8..501abd7 100644
--- a/valuescript_common/src/instruction_byte.rs
+++ b/valuescript_common/src/instruction_byte.rs
@@ -54,6 +54,7 @@ pub enum InstructionByte {
   ThisSubCall = 0x33,
   Next = 0x34,
   UnpackIterRes = 0x35,
+  Cat = 0x36,
 }
 
 impl InstructionByte {
@@ -115,6 +116,7 @@ impl InstructionByte {
       0x33 => ThisSubCall,
       0x34 => Next,
       0x35 => UnpackIterRes,
+      0x36 => Cat,
 
       _ => panic!("Unrecognized instruction: {}", byte),
     };
diff --git a/valuescript_compiler/src/asm.rs b/valuescript_compiler/src/asm.rs
index 5846529..f8b4455 100644
--- a/valuescript_compiler/src/asm.rs
+++ b/valuescript_compiler/src/asm.rs
@@ -292,6 +292,7 @@ pub enum Instruction {
   ThisSubCall(Value, Value, Value, Register),
   Next(Register, Register),
   UnpackIterRes(Register, Register, Register),
+  Cat(Value, Register),
 }
 
 impl std::fmt::Display for Instruction {
@@ -457,6 +458,9 @@ impl std::fmt::Display for Instruction {
           obj, value_register, done_register
         )
       }
+      Instruction::Cat(iterables, register) => {
+        write!(f, "cat {} {}", iterables, register)
+      }
     }
   }
 }
@@ -521,6 +525,7 @@ impl Instruction {
       ThisSubCall(..) => InstructionByte::ThisSubCall,
       Next(..) => InstructionByte::Next,
       UnpackIterRes(..) => InstructionByte::UnpackIterRes,
+      Cat(..) => InstructionByte::Cat,
     }
   }
 }
diff --git a/valuescript_compiler/src/assembler.rs b/valuescript_compiler/src/assembler.rs
index be613fe..0274551 100644
--- a/valuescript_compiler/src/assembler.rs
+++ b/valuescript_compiler/src/assembler.rs
@@ -240,6 +240,10 @@ impl Assembler {
         self.register(value_dst);
         self.register(done_dst);
       }
+      Cat(iterables, dst) => {
+        self.value(iterables);
+        self.register(dst);
+      }
     }
   }
 
diff --git a/valuescript_compiler/src/assembly_parser.rs b/valuescript_compiler/src/assembly_parser.rs
index 30e03a8..5f628ad 100644
--- a/valuescript_compiler/src/assembly_parser.rs
+++ b/valuescript_compiler/src/assembly_parser.rs
@@ -229,6 +229,7 @@ impl<'a> AssemblyParser<'a> {
       ("this_subcall", InstructionByte::ThisSubCall),
       ("next", InstructionByte::Next),
       ("unpack_iter_res", InstructionByte::UnpackIterRes),
+      ("cat", InstructionByte::Cat),
     ]);
 
     for (word, instruction) in instruction_word_map {
@@ -693,6 +694,7 @@ impl<'a> AssemblyParser<'a> {
         self.assemble_register(),
         self.assemble_register(),
       ),
+      Cat => Instruction::Cat(self.assemble_value(), self.assemble_register()),
     }
   }
 
diff --git a/valuescript_compiler/src/instruction_mutates_this.rs b/valuescript_compiler/src/instruction_mutates_this.rs
index ad9edef..96041b2 100644
--- a/valuescript_compiler/src/instruction_mutates_this.rs
+++ b/valuescript_compiler/src/instruction_mutates_this.rs
@@ -48,7 +48,8 @@ pub fn instruction_mutates_this(instruction: &Instruction) -> bool {
     | ImportStar(_, reg)
     | SetCatch(_, reg)
     | ConstSubCall(_, _, _, reg)
-    | ThisSubCall(_, _, _, reg) => reg == &Register::This,
+    | ThisSubCall(_, _, _, reg)
+    | Cat(_, reg) => reg == &Register::This,
 
     Next(iter, res) => iter == &Register::This || res == &Register::This,
     UnpackIterRes(_, value_reg, done_reg) => {
diff --git a/valuescript_compiler/src/link_module.rs b/valuescript_compiler/src/link_module.rs
index 5b02c74..1ea5c0e 100644
--- a/valuescript_compiler/src/link_module.rs
+++ b/valuescript_compiler/src/link_module.rs
@@ -244,7 +244,8 @@ where
       | UnaryMinus(arg, _)
       | Import(arg, _)
       | ImportStar(arg, _)
-      | Throw(arg) => {
+      | Throw(arg)
+      | Cat(arg, _) => {
         self.value(Some(owner), arg);
       }
       OpPlus(arg1, arg2, _)
diff --git a/valuescript_vm/src/bytecode_stack_frame.rs b/valuescript_vm/src/bytecode_stack_frame.rs
index d790c68..26372d6 100644
--- a/valuescript_vm/src/bytecode_stack_frame.rs
+++ b/valuescript_vm/src/bytecode_stack_frame.rs
@@ -519,6 +519,34 @@ impl StackFrameTrait for BytecodeStackFrame {
             operations::op_sub(self.registers[iter_res_i].clone(), "done".to_val())?;
         }
       }
+
+      Cat => {
+        let mut vals = Vec::<Val>::new();
+
+        let bytecode_type = self.decoder.decode_type();
+
+        if bytecode_type != BytecodeType::Array {
+          panic!("Not implemented: cat instruction not using inline array");
+        }
+
+        while self.decoder.peek_type() != BytecodeType::End {
+          let iterable = self.decoder.decode_val(&self.registers);
+
+          match iterable {
+            Val::Array(array_data) => {
+              for item in &array_data.elements {
+                vals.push(item.clone());
+              }
+            }
+            _ => todo!("Cat: Non-array iterable"),
+          }
+        }
+
+        // TODO: Just skip the byte in release builds?
+        assert!(self.decoder.decode_type() == BytecodeType::End);
+
+        self.registers[self.decoder.decode_register_index().unwrap()] = vals.to_val();
+      }
     };
 
     Ok(FrameStepOk::Continue)