diff --git a/README.md b/README.md
index 7093f0b..8589b3b 100644
--- a/README.md
+++ b/README.md
@@ -38,6 +38,8 @@
      *    [Parent Parsers](#parent-parsers)
      *    [Subcommands](#subcommands)
      *    [Parse Known Args](#parse-known-args)
+     *    [Custom Prefix Characters](#custom-prefix-characters)
+     *    [Custom Assignment Characters](#custom-assignment-characters)
 *    [Further Examples](#further-examples)
      *    [Construct a JSON object from a filename argument](#construct-a-json-object-from-a-filename-argument)
      *    [Positional Arguments with Compound Toggle Arguments](#positional-arguments-with-compound-toggle-arguments)
@@ -823,6 +825,97 @@ int main(int argc, char *argv[]) {
 }
 ```
 
+### Custom Prefix Characters 
+
+Most command-line options will use `-` as the prefix, e.g. `-f/--foo`. Parsers that need to support different or additional prefix characters, e.g. for options like `+f` or `/foo`, may specify them using the `set_prefix_chars()`.
+
+The default prefix character is `-`.
+
+```cpp
+#include <argparse/argparse.hpp>
+#include <cassert>
+
+int main(int argc, char *argv[]) {
+  argparse::ArgumentParser program("test");
+  program.set_prefix_chars("-+/");
+
+  program.add_argument("+f");
+  program.add_argument("--bar");
+  program.add_argument("/foo");
+
+  try {
+    program.parse_args(argc, argv);
+  }
+  catch (const std::runtime_error& err) {
+    std::cerr << err.what() << std::endl;
+    std::cerr << program;
+    std::exit(1);
+  }
+
+  if (program.is_used("+f")) {
+    std::cout << "+f    : " << program.get("+f") << "\n";
+  }
+
+  if (program.is_used("--bar")) {
+    std::cout << "--bar : " << program.get("--bar") << "\n";
+  }
+
+  if (program.is_used("/foo")) {
+    std::cout << "/foo  : " << program.get("/foo") << "\n";
+  }  
+}
+```
+
+```console
+foo@bar:/home/dev/$ ./main +f 5 --bar 3.14f /foo "Hello"
++f    : 5
+--bar : 3.14f
+/foo  : Hello
+```
+
+### Custom Assignment Characters 
+
+In addition to prefix characters, custom 'assign' characters can be set. This setting is used to allow invocations like `./test --foo=Foo /B:Bar`.
+
+The default assign character is `=`.
+
+```cpp
+#include <argparse/argparse.hpp>
+#include <cassert>
+
+int main(int argc, char *argv[]) {
+  argparse::ArgumentParser program("test");
+  program.set_prefix_chars("-+/");
+  program.set_assign_chars("=:");
+
+  program.add_argument("--foo");
+  program.add_argument("/B");
+
+  try {
+    program.parse_args(argc, argv);
+  }
+  catch (const std::runtime_error& err) {
+    std::cerr << err.what() << std::endl;
+    std::cerr << program;
+    std::exit(1);
+  }
+
+  if (program.is_used("--foo")) {
+    std::cout << "--foo : " << program.get("--foo") << "\n";
+  }
+
+  if (program.is_used("/B")) {
+    std::cout << "/B    : " << program.get("/B") << "\n";
+  }
+}
+```
+
+```console
+foo@bar:/home/dev/$ ./main --foo=Foo /B:Bar
+--foo : Foo
+/B    : Bar
+```
+
 ## Further Examples
 
 ### Construct a JSON object from a filename argument
diff --git a/include/argparse/argparse.hpp b/include/argparse/argparse.hpp
index c0e13dd..ba27b43 100644
--- a/include/argparse/argparse.hpp
+++ b/include/argparse/argparse.hpp
@@ -355,10 +355,12 @@ class Argument {
       -> std::ostream &;
 
   template <std::size_t N, std::size_t... I>
-  explicit Argument(std::array<std::string_view, N> &&a,
+  explicit Argument(std::string_view prefix_chars,
+                    std::array<std::string_view, N> &&a,
                     std::index_sequence<I...> /*unused*/)
-      : m_is_optional((is_optional(a[I]) || ...)), m_is_required(false),
-        m_is_repeatable(false), m_is_used(false) {
+      : m_is_optional((is_optional(a[I], prefix_chars) || ...)),
+        m_is_required(false), m_is_repeatable(false), m_is_used(false),
+        m_prefix_chars(prefix_chars) {
     ((void)m_names.emplace_back(a[I]), ...);
     std::sort(
         m_names.begin(), m_names.end(), [](const auto &lhs, const auto &rhs) {
@@ -368,8 +370,9 @@ class Argument {
 
 public:
   template <std::size_t N>
-  explicit Argument(std::array<std::string_view, N> &&a)
-      : Argument(std::move(a), std::make_index_sequence<N>{}) {}
+  explicit Argument(std::string_view prefix_chars,
+                    std::array<std::string_view, N> &&a)
+      : Argument(prefix_chars, std::move(a), std::make_index_sequence<N>{}) {}
 
   Argument &help(std::string help_text) {
     m_help = std::move(help_text);
@@ -513,7 +516,9 @@ public:
                                    num_args_max));
       }
       if (!m_accepts_optional_like_value) {
-        end = std::find_if(start, end, Argument::is_optional);
+        end = std::find_if(
+            start, end,
+            std::bind(is_optional, std::placeholders::_1, m_prefix_chars));
         dist = static_cast<std::size_t>(std::distance(start, end));
         if (dist < num_args_min) {
           throw std::runtime_error("Too few arguments");
@@ -821,8 +826,9 @@ private:
     return false;
   }
 
-  static bool is_optional(std::string_view name) {
-    return !is_positional(name);
+  static bool is_optional(std::string_view name,
+                          std::string_view prefix_chars) {
+    return !is_positional(name, prefix_chars);
   }
 
   /*
@@ -832,20 +838,21 @@ private:
    *    '-' decimal-literal
    *    !'-' anything
    */
-  static bool is_positional(std::string_view name) {
-    switch (lookahead(name)) {
-    case eof:
+  static bool is_positional(std::string_view name,
+                            std::string_view prefix_chars) {
+    auto first = lookahead(name);
+
+    if (first == eof) {
       return true;
-    case '-': {
+    } else if (prefix_chars.find(static_cast<char>(first)) !=
+               std::string_view::npos) {
       name.remove_prefix(1);
       if (name.empty()) {
         return true;
       }
       return is_decimal_literal(name);
     }
-    default:
-      return true;
-    }
+    return true;
   }
 
   /*
@@ -921,6 +928,7 @@ private:
   bool m_is_required : true;
   bool m_is_repeatable : true;
   bool m_is_used : true; // True if the optional argument is used by user
+  std::string_view m_prefix_chars; // ArgumentParser has the prefix_chars
 };
 
 class ArgumentParser {
@@ -960,7 +968,8 @@ public:
   ArgumentParser(const ArgumentParser &other)
       : m_program_name(other.m_program_name), m_version(other.m_version),
         m_description(other.m_description), m_epilog(other.m_epilog),
-        m_is_parsed(other.m_is_parsed),
+        m_prefix_chars(other.m_prefix_chars),
+        m_assign_chars(other.m_assign_chars), m_is_parsed(other.m_is_parsed),
         m_positional_arguments(other.m_positional_arguments),
         m_optional_arguments(other.m_optional_arguments),
         m_parser_path(other.m_parser_path), m_subparsers(other.m_subparsers) {
@@ -991,8 +1000,9 @@ public:
   // Call add_argument with variadic number of string arguments
   template <typename... Targs> Argument &add_argument(Targs... f_args) {
     using array_of_sv = std::array<std::string_view, sizeof...(Targs)>;
-    auto argument = m_optional_arguments.emplace(
-        std::cend(m_optional_arguments), array_of_sv{f_args...});
+    auto argument =
+        m_optional_arguments.emplace(std::cend(m_optional_arguments),
+                                     m_prefix_chars, array_of_sv{f_args...});
 
     if (!argument->m_is_optional) {
       m_positional_arguments.splice(std::cend(m_positional_arguments),
@@ -1032,6 +1042,16 @@ public:
     return *this;
   }
 
+  ArgumentParser &set_prefix_chars(std::string prefix_chars) {
+    m_prefix_chars = std::move(prefix_chars);
+    return *this;
+  }
+
+  ArgumentParser &set_assign_chars(std::string assign_chars) {
+    m_assign_chars = std::move(assign_chars);
+    return *this;
+  }
+
   /* Call parse_args_internal - which does all the work
    * Then, validate the parsed arguments
    * This variant is used mainly for testing
@@ -1126,16 +1146,19 @@ public:
     if (it != m_argument_map.end()) {
       return *(it->second);
     }
-    if (arg_name.front() != '-') {
+    if (!is_valid_prefix_char(arg_name.front())) {
       std::string name(arg_name);
+      const auto legal_prefix_char = get_any_valid_prefix_char();
+      const auto prefix = std::string(1, legal_prefix_char);
+
       // "-" + arg_name
-      name = "-" + name;
+      name = prefix + name;
       it = m_argument_map.find(name);
       if (it != m_argument_map.end()) {
         return *(it->second);
       }
       // "--" + arg_name
-      name = "-" + name;
+      name = prefix + name;
       it = m_argument_map.find(name);
       if (it != m_argument_map.end()) {
         return *(it->second);
@@ -1226,28 +1249,68 @@ public:
   }
 
 private:
+  bool is_valid_prefix_char(char c) const {
+    return m_prefix_chars.find(c) != std::string::npos;
+  }
+
+  char get_any_valid_prefix_char() const { return m_prefix_chars[0]; }
+
   /*
    * Pre-process this argument list. Anything starting with "--", that
    * contains an =, where the prefix before the = has an entry in the
    * options table, should be split.
    */
   std::vector<std::string>
-  preprocess_arguments(const std::vector<std::string> &raw_arguments) {
-    std::vector<std::string> arguments;
+  preprocess_arguments(const std::vector<std::string> &raw_arguments) const {
+    std::vector<std::string> arguments{};
     for (const auto &arg : raw_arguments) {
+
+      const auto argument_starts_with_prefix_chars =
+          [this](const std::string &a) -> bool {
+        if (!a.empty()) {
+
+          const auto legal_prefix = [this](char c) -> bool {
+            return m_prefix_chars.find(c) != std::string::npos;
+          };
+
+          // Windows-style
+          // if '/' is a legal prefix char
+          // then allow single '/' followed by argument name, followed by an
+          // assign char, e.g., ':' e.g., 'test.exe /A:Foo'
+          const auto windows_style = legal_prefix('/');
+
+          if (windows_style) {
+            if (legal_prefix(a[0])) {
+              return true;
+            }
+          } else {
+            // Slash '/' is not a legal prefix char
+            // For all other characters, only support long arguments
+            // i.e., the argument must start with 2 prefix chars, e.g,
+            // '--foo' e,g, './test --foo=Bar -DARG=yes'
+            if (a.size() > 1) {
+              return (legal_prefix(a[0]) && legal_prefix(a[1]));
+            }
+          }
+        }
+        return false;
+      };
+
       // Check that:
       // - We don't have an argument named exactly this
-      // - The argument starts with "--"
-      // - The argument contains a "="
-      std::size_t eqpos = arg.find("=");
+      // - The argument starts with a prefix char, e.g., "--"
+      // - The argument contains an assign char, e.g., "="
+      auto assign_char_pos = arg.find_first_of(m_assign_chars);
+
       if (m_argument_map.find(arg) == m_argument_map.end() &&
-          arg.rfind("--", 0) == 0 && eqpos != std::string::npos) {
+          argument_starts_with_prefix_chars(arg) &&
+          assign_char_pos != std::string::npos) {
         // Get the name of the potential option, and check it exists
-        std::string opt_name = arg.substr(0, eqpos);
+        std::string opt_name = arg.substr(0, assign_char_pos);
         if (m_argument_map.find(opt_name) != m_argument_map.end()) {
           // This is the name of an option! Split it into two parts
           arguments.push_back(std::move(opt_name));
-          arguments.push_back(arg.substr(eqpos + 1));
+          arguments.push_back(arg.substr(assign_char_pos + 1));
           continue;
         }
       }
@@ -1269,7 +1332,7 @@ private:
     auto positional_argument_it = std::begin(m_positional_arguments);
     for (auto it = std::next(std::begin(arguments)); it != end;) {
       const auto &current_argument = *it;
-      if (Argument::is_positional(current_argument)) {
+      if (Argument::is_positional(current_argument, m_prefix_chars)) {
         if (positional_argument_it == std::end(m_positional_arguments)) {
 
           std::string_view maybe_command = current_argument;
@@ -1302,8 +1365,9 @@ private:
         auto argument = arg_map_it->second;
         it = argument->consume(std::next(it), end, arg_map_it->first);
       } else if (const auto &compound_arg = current_argument;
-                 compound_arg.size() > 1 && compound_arg[0] == '-' &&
-                 compound_arg[1] != '-') {
+                 compound_arg.size() > 1 &&
+                 is_valid_prefix_char(compound_arg[0]) &&
+                 !is_valid_prefix_char(compound_arg[1])) {
         ++it;
         for (std::size_t j = 1; j < compound_arg.size(); j++) {
           auto hypothetical_arg = std::string{'-', compound_arg[j]};
@@ -1338,7 +1402,7 @@ private:
     auto positional_argument_it = std::begin(m_positional_arguments);
     for (auto it = std::next(std::begin(arguments)); it != end;) {
       const auto &current_argument = *it;
-      if (Argument::is_positional(current_argument)) {
+      if (Argument::is_positional(current_argument, m_prefix_chars)) {
         if (positional_argument_it == std::end(m_positional_arguments)) {
 
           std::string_view maybe_command = current_argument;
@@ -1375,8 +1439,9 @@ private:
         auto argument = arg_map_it->second;
         it = argument->consume(std::next(it), end, arg_map_it->first);
       } else if (const auto &compound_arg = current_argument;
-                 compound_arg.size() > 1 && compound_arg[0] == '-' &&
-                 compound_arg[1] != '-') {
+                 compound_arg.size() > 1 &&
+                 is_valid_prefix_char(compound_arg[0]) &&
+                 !is_valid_prefix_char(compound_arg[1])) {
         ++it;
         for (std::size_t j = 1; j < compound_arg.size(); j++) {
           auto hypothetical_arg = std::string{'-', compound_arg[j]};
@@ -1429,6 +1494,8 @@ private:
   std::string m_version;
   std::string m_description;
   std::string m_epilog;
+  std::string m_prefix_chars{"-"};
+  std::string m_assign_chars{"="};
   bool m_is_parsed = false;
   std::list<Argument> m_positional_arguments;
   std::list<Argument> m_optional_arguments;
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index b61040f..b228feb 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -49,6 +49,7 @@ file(GLOB ARGPARSE_TEST_SOURCES
     test_subparsers.cpp
     test_parse_known_args.cpp
     test_equals_form.cpp
+    test_prefix_chars.cpp
 )
 set_source_files_properties(main.cpp
     PROPERTIES
diff --git a/test/test_prefix_chars.cpp b/test/test_prefix_chars.cpp
new file mode 100644
index 0000000..e62b1d9
--- /dev/null
+++ b/test/test_prefix_chars.cpp
@@ -0,0 +1,41 @@
+#include <argparse/argparse.hpp>
+#include <cmath>
+#include <doctest.hpp>
+
+using doctest::test_suite;
+
+TEST_CASE("Parse with custom prefix chars" * test_suite("prefix_chars")) {
+  argparse::ArgumentParser program("test");
+  program.set_prefix_chars("-+");
+  program.add_argument("+f");
+  program.add_argument("++bar");
+  program.parse_args({"test", "+f", "X", "++bar", "Y"});
+  REQUIRE(program.get("+f") == "X");
+  REQUIRE(program.get("++bar") == "Y");
+}
+
+TEST_CASE("Parse with custom Windows-style prefix chars" *
+          test_suite("prefix_chars")) {
+  argparse::ArgumentParser program("dir");
+  program.set_prefix_chars("/");
+  program.add_argument("/A").nargs(1);
+  program.add_argument("/B").default_value(false).implicit_value(true);
+  program.add_argument("/C").default_value(false).implicit_value(true);
+  program.parse_args({"dir", "/A", "D", "/B", "/C"});
+  REQUIRE(program.get("/A") == "D");
+  REQUIRE(program.get<bool>("/B") == true);
+}
+
+TEST_CASE("Parse with custom Windows-style prefix chars and assign chars" *
+          test_suite("prefix_chars")) {
+  argparse::ArgumentParser program("dir");
+  program.set_prefix_chars("/");
+  program.set_assign_chars(":=");
+  program.add_argument("/A").nargs(1);
+  program.add_argument("/B").nargs(1);
+  program.add_argument("/C").default_value(false).implicit_value(true);
+  program.parse_args({"dir", "/A:D", "/B=Boo", "/C"});
+  REQUIRE(program.get("/A") == "D");
+  REQUIRE(program.get("/B") == "Boo");
+  REQUIRE(program.get<bool>("/C") == true);
+}
\ No newline at end of file