diff --git a/include/natalie/object.hpp b/include/natalie/object.hpp
index b63733b333..a50000510b 100644
--- a/include/natalie/object.hpp
+++ b/include/natalie/object.hpp
@@ -279,6 +279,7 @@ class Object : public Cell {
 
     ArrayObject *to_ary(Env *env);
     IntegerObject *to_int(Env *env);
+    StringObject *to_str(Env *env);
 
 protected:
     ClassObject *m_klass { nullptr };
diff --git a/include/natalie/string_object.hpp b/include/natalie/string_object.hpp
index becc5d7431..e9d12b6488 100644
--- a/include/natalie/string_object.hpp
+++ b/include/natalie/string_object.hpp
@@ -146,7 +146,8 @@ class StringObject : public Object {
         return this;
     }
 
-    bool start_with(Env *, Value) const;
+    bool internal_start_with(Env *, Value) const;
+    bool start_with(Env *, size_t, Value *) const;
     bool end_with(Env *, Value) const;
     bool is_empty() const { return m_string.is_empty(); }
 
diff --git a/lib/natalie/compiler/binding_gen.rb b/lib/natalie/compiler/binding_gen.rb
index a5e8712cfe..3f748dc760 100644
--- a/lib/natalie/compiler/binding_gen.rb
+++ b/lib/natalie/compiler/binding_gen.rb
@@ -869,7 +869,7 @@ def generate_name
 gen.binding('String', 'rstrip!', 'StringObject', 'rstrip_in_place', argc: 0, pass_env: true, pass_block: false, return_type: :Object)
 gen.binding('String', 'size', 'StringObject', 'size', argc: 0, pass_env: true, pass_block: false, return_type: :Object)
 gen.binding('String', 'split', 'StringObject', 'split', argc: 0..2, pass_env: true, pass_block: false, return_type: :Object)
-gen.binding('String', 'start_with?', 'StringObject', 'start_with', argc: 1, pass_env: true, pass_block: false, return_type: :bool)
+gen.binding('String', 'start_with?', 'StringObject', 'start_with', argc: :any, pass_env: true, pass_block: false, return_type: :bool)
 gen.binding('String', 'strip', 'StringObject', 'strip', argc: 0, pass_env: true, pass_block: false, return_type: :Object)
 gen.binding('String', 'strip!', 'StringObject', 'strip_in_place', argc: 0, pass_env: true, pass_block: false, return_type: :Object)
 gen.binding('String', 'sub', 'StringObject', 'sub', argc: 1..2, pass_env: true, pass_block: true, return_type: :Object)
diff --git a/spec/core/string/start_with_spec.rb b/spec/core/string/start_with_spec.rb
new file mode 100644
index 0000000000..aaed197ff3
--- /dev/null
+++ b/spec/core/string/start_with_spec.rb
@@ -0,0 +1,8 @@
+# -*- encoding: utf-8 -*-
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+require_relative '../../shared/string/start_with'
+
+describe "String#start_with?" do
+  it_behaves_like :start_with, :to_s
+end
diff --git a/spec/shared/string/start_with.rb b/spec/shared/string/start_with.rb
new file mode 100644
index 0000000000..d6448a1c45
--- /dev/null
+++ b/spec/shared/string/start_with.rb
@@ -0,0 +1,75 @@
+describe :start_with, shared: true do
+  # the @method should either be :to_s or :to_sym
+
+  it "returns true only if beginning match" do
+    s = "hello".send(@method)
+    s.should.start_with?('h')
+    s.should.start_with?('hel')
+    s.should_not.start_with?('el')
+  end
+
+  it "returns true only if any beginning match" do
+    "hello".send(@method).should.start_with?('x', 'y', 'he', 'z')
+  end
+
+  it "returns true if the search string is empty" do
+    "hello".send(@method).should.start_with?("")
+    "".send(@method).should.start_with?("")
+  end
+
+  it "converts its argument using :to_str" do
+    s = "hello".send(@method)
+    find = mock('h')
+    find.should_receive(:to_str).and_return("h")
+    s.should.start_with?(find)
+  end
+
+  it "ignores arguments not convertible to string" do
+    "hello".send(@method).should_not.start_with?()
+    -> { "hello".send(@method).start_with?(1) }.should raise_error(TypeError)
+    -> { "hello".send(@method).start_with?(["h"]) }.should raise_error(TypeError)
+    -> { "hello".send(@method).start_with?(1, nil, "h") }.should raise_error(TypeError)
+  end
+
+  it "uses only the needed arguments" do
+    find = mock('h')
+    find.should_not_receive(:to_str)
+    "hello".send(@method).should.start_with?("h",find)
+  end
+
+  it "works for multibyte strings" do
+    "céréale".send(@method).should.start_with?("cér")
+  end
+
+  # NATFIXME: Add support for regexps
+  xit "supports regexps" do
+    regexp = /[h1]/
+    "hello".send(@method).should.start_with?(regexp)
+    "1337".send(@method).should.start_with?(regexp)
+    "foxes are 1337".send(@method).should_not.start_with?(regexp)
+    "chunky\n12bacon".send(@method).should_not.start_with?(/12/)
+  end
+
+  # NATFIXME: Add support for regexps
+  xit "supports regexps with ^ and $ modifiers" do
+    regexp1 = /^\d{2}/
+    regexp2 = /\d{2}$/
+    "12test".send(@method).should.start_with?(regexp1)
+    "test12".send(@method).should_not.start_with?(regexp1)
+    "12test".send(@method).should_not.start_with?(regexp2)
+    "test12".send(@method).should_not.start_with?(regexp2)
+  end
+
+  # NATFIXME: Add support for regexps
+  xit "sets Regexp.last_match if it returns true" do
+    regexp = /test-(\d+)/
+    "test-1337".send(@method).start_with?(regexp).should be_true
+    Regexp.last_match.should_not be_nil
+    Regexp.last_match[1].should == "1337"
+    $1.should == "1337"
+
+    "test-asdf".send(@method).start_with?(regexp).should be_false
+    Regexp.last_match.should be_nil
+    $1.should be_nil
+  end
+end
diff --git a/src/object.cpp b/src/object.cpp
index a34c863b09..5712d01e26 100644
--- a/src/object.cpp
+++ b/src/object.cpp
@@ -878,4 +878,24 @@ IntegerObject *Object::to_int(Env *env) {
         result->klass()->inspect_str());
 }
 
+StringObject *Object::to_str(Env *env) {
+    if (is_string()) return as_string();
+
+    auto to_str = "to_str"_s;
+    if (! respond_to(env, to_str)) {
+        assert_type(env, Type::String, "String");
+    }
+
+    auto result = send(env, to_str);
+
+    if (result->is_string())
+        return result->as_string();
+
+    env->raise(
+       "TypeError", "can't convert {} to String ({}#to_str gives {})",
+        klass()->inspect_str(),
+        klass()->inspect_str(),
+        result->klass()->inspect_str());
+}
+
 }
diff --git a/src/string_object.cpp b/src/string_object.cpp
index 0170a9cce5..d7c01e182f 100644
--- a/src/string_object.cpp
+++ b/src/string_object.cpp
@@ -198,11 +198,23 @@ StringObject *StringObject::successive(Env *env) {
     return new StringObject { str };
 }
 
-bool StringObject::start_with(Env *env, Value needle) const {
+bool StringObject::internal_start_with(Env *env, Value needle) const {
     nat_int_t i = index_int(env, needle, 0);
+
     return i == 0;
 }
 
+bool StringObject::start_with(Env *env, size_t argc, Value *args) const {
+    for (size_t i = 0; i < argc; ++i) {
+        auto arg = args[i];
+
+        if (internal_start_with(env, arg))
+            return true;
+    }
+    
+    return false;
+}
+
 bool StringObject::end_with(Env *env, Value needle) const {
     needle->assert_type(env, Object::Type::String, "String");
     if (length() < needle->as_string()->length())
@@ -233,8 +245,9 @@ Value StringObject::index(Env *env, Value needle, size_t start) {
 }
 
 nat_int_t StringObject::index_int(Env *env, Value needle, size_t start) const {
-    needle->assert_type(env, Object::Type::String, "String");
-    const char *ptr = strstr(c_str() + start, needle->as_string()->c_str());
+    auto needle_str = needle->to_str(env)->as_string()->c_str();
+
+    const char *ptr = strstr(c_str() + start, needle_str);
     if (ptr == nullptr)
         return -1;
     return ptr - c_str();
diff --git a/src/symbol_object.cpp b/src/symbol_object.cpp
index 928253b021..b3b19613d9 100644
--- a/src/symbol_object.cpp
+++ b/src/symbol_object.cpp
@@ -82,7 +82,7 @@ Value SymbolObject::cmp(Env *env, Value other_value) {
 }
 
 bool SymbolObject::start_with(Env *env, Value needle) {
-    return to_s(env)->start_with(env, needle);
+    return to_s(env)->internal_start_with(env, needle);
 }
 
 Value SymbolObject::ref(Env *env, Value index_obj) {