diff --git a/core/src/avm1/globals.rs b/core/src/avm1/globals.rs
index fd40d18f7..84844fad3 100644
--- a/core/src/avm1/globals.rs
+++ b/core/src/avm1/globals.rs
@@ -19,6 +19,7 @@ pub(crate) mod movie_clip;
 mod object;
 mod sound;
 mod stage;
+mod string;
 pub(crate) mod text_field;
 mod xml;
 
@@ -140,6 +141,7 @@ pub struct SystemPrototypes<'gc> {
     pub text_field: Object<'gc>,
     pub array: Object<'gc>,
     pub xml_node: Object<'gc>,
+    pub string: Object<'gc>,
 }
 
 unsafe impl<'gc> gc_arena::Collect for SystemPrototypes<'gc> {
@@ -152,6 +154,7 @@ unsafe impl<'gc> gc_arena::Collect for SystemPrototypes<'gc> {
         self.text_field.trace(cc);
         self.array.trace(cc);
         self.xml_node.trace(cc);
+        self.string.trace(cc);
     }
 }
 
@@ -180,6 +183,8 @@ pub fn create_globals<'gc>(
 
     let xml_proto: Object<'gc> = xml::create_xml_proto(gc_context, xmlnode_proto, function_proto);
 
+    let string_proto: Object<'gc> = string::create_proto(gc_context, object_proto, function_proto);
+
     //TODO: These need to be constructors and should also set `.prototype` on each one
     let object = ScriptObject::function(
         gc_context,
@@ -236,6 +241,12 @@ pub fn create_globals<'gc>(
         Some(function_proto),
         Some(xml_proto),
     );
+    let string = ScriptObject::function(
+        gc_context,
+        Executable::Native(string::string_constructor),
+        Some(function_proto),
+        Some(string_proto),
+    );
 
     let listeners = SystemListeners::new(gc_context, Some(array_proto));
 
@@ -249,6 +260,7 @@ pub fn create_globals<'gc>(
     globals.define_value(gc_context, "TextField", text_field.into(), EnumSet::empty());
     globals.define_value(gc_context, "XMLNode", xmlnode.into(), EnumSet::empty());
     globals.define_value(gc_context, "XML", xml.into(), EnumSet::empty());
+    globals.define_value(gc_context, "String", string.into(), EnumSet::empty());
     globals.force_set_function(
         "Number",
         number,
@@ -357,6 +369,7 @@ pub fn create_globals<'gc>(
             text_field: text_field_proto,
             array: array_proto,
             xml_node: xmlnode_proto,
+            string: string_proto,
         },
         globals.into(),
         listeners,
diff --git a/core/src/avm1/globals/string.rs b/core/src/avm1/globals/string.rs
new file mode 100644
index 000000000..8ca2ead8c
--- /dev/null
+++ b/core/src/avm1/globals/string.rs
@@ -0,0 +1,90 @@
+//! `String` class impl
+
+use crate::avm1::return_value::ReturnValue;
+use crate::avm1::value_object::ValueObject;
+use crate::avm1::{Avm1, Error, Object, TObject, Value};
+use crate::context::UpdateContext;
+use enumset::EnumSet;
+use gc_arena::MutationContext;
+
+/// `String` constructor
+pub fn string_constructor<'gc>(
+    avm: &mut Avm1<'gc>,
+    ac: &mut UpdateContext<'_, 'gc, '_>,
+    this: Object<'gc>,
+    args: &[Value<'gc>],
+) -> Result<ReturnValue<'gc>, Error> {
+    let arg = args
+        .get(0)
+        .cloned()
+        .unwrap_or(Value::Undefined)
+        .coerce_to_string(avm, ac)?;
+
+    if let Some(mut vbox) = this.as_value_object() {
+        vbox.replace_value(ac.gc_context, arg.into());
+    }
+
+    Ok(Value::Undefined.into())
+}
+
+/// `String.toString` / `String.valueOf` impl
+pub fn to_string_value_of<'gc>(
+    avm: &mut Avm1<'gc>,
+    ac: &mut UpdateContext<'_, 'gc, '_>,
+    this: Object<'gc>,
+    _args: &[Value<'gc>],
+) -> Result<ReturnValue<'gc>, Error> {
+    if let Some(vbox) = this.as_value_object() {
+        return Ok(vbox.unbox().coerce_to_string(avm, ac)?.into());
+    }
+
+    //TODO: This normally falls back to `[object Object]` or `[type Function]`,
+    //implying that `toString` and `valueOf` are inherent object properties and
+    //not just methods.
+    Ok(Value::Undefined.into())
+}
+
+/// `String.toUpperCase` impl
+pub fn to_upper_case<'gc>(
+    avm: &mut Avm1<'gc>,
+    ac: &mut UpdateContext<'_, 'gc, '_>,
+    this: Object<'gc>,
+    _args: &[Value<'gc>],
+) -> Result<ReturnValue<'gc>, Error> {
+    let sval = Value::Object(this).coerce_to_string(avm, ac)?;
+
+    Ok(sval.to_uppercase().into())
+}
+
+/// `String.prototype` definition
+pub fn create_proto<'gc>(
+    gc_context: MutationContext<'gc, '_>,
+    proto: Object<'gc>,
+    fn_proto: Object<'gc>,
+) -> Object<'gc> {
+    let string_proto = ValueObject::empty_box(gc_context, Some(proto));
+
+    string_proto.as_script_object().unwrap().force_set_function(
+        "toString",
+        to_string_value_of,
+        gc_context,
+        EnumSet::empty(),
+        Some(fn_proto),
+    );
+    string_proto.as_script_object().unwrap().force_set_function(
+        "valueOf",
+        to_string_value_of,
+        gc_context,
+        EnumSet::empty(),
+        Some(fn_proto),
+    );
+    string_proto.as_script_object().unwrap().force_set_function(
+        "toUpperCase",
+        to_upper_case,
+        gc_context,
+        EnumSet::empty(),
+        Some(fn_proto),
+    );
+
+    string_proto
+}
diff --git a/core/src/avm1/value_object.rs b/core/src/avm1/value_object.rs
index 8fe33a165..bf1198d5f 100644
--- a/core/src/avm1/value_object.rs
+++ b/core/src/avm1/value_object.rs
@@ -42,16 +42,21 @@ impl<'gc> ValueObject<'gc> {
     pub fn boxed(
         gc_context: MutationContext<'gc, '_>,
         value: Value<'gc>,
-        _system_prototypes: &SystemPrototypes<'gc>,
+        system_prototypes: &SystemPrototypes<'gc>,
     ) -> Object<'gc> {
         if let Value::Object(ob) = value {
             ob
         } else {
+            let proto = match value {
+                Value::String(_) => Some(system_prototypes.string),
+                _ => None,
+            };
+
             ValueObject(GcCell::allocate(
                 gc_context,
                 ValueObjectData {
-                    base: ScriptObject::object(gc_context, None),
-                    value: value,
+                    base: ScriptObject::object(gc_context, proto),
+                    value,
                 },
             ))
             .into()