diff --git a/src/argparse.rs b/src/argparse.rs
index dd2db87..55c35e8 100644
--- a/src/argparse.rs
+++ b/src/argparse.rs
@@ -37,6 +37,7 @@ pub enum ParseError<'a> {
   //TODO
   //Exclusive(&'static str, &'a str),
   RequiredPositional(&'static str),
+  RequiredParameter(&'static str),
 }
 
 /// The type of parsing error
@@ -63,6 +64,7 @@ impl core::fmt::Display for ParseError<'_> {
         => write!(f, "Argument for option '{o}' cannot be empty"),
       //Self::Exclusive(l, r) => write!(f, "Argument {l}: not allowed with argument {r}"),
       Self::RequiredPositional(o) => write!(f, "Missing required positional argument '{o}'"),
+      Self::RequiredParameter(o) => write!(f, "Missing required option '{o}'"),
     }
   }
 }
@@ -92,17 +94,21 @@ impl From<core::num::ParseFloatError> for ParseError<'_> {
 
 impl core::error::Error for ParseError<'_> {}
 
+type RequiredParamsBitSet = ordered_bitset::OrderedBitSet<BitSetType, BITSET_SLOTS>;
+
 /// Internal state tracked by the parser
 struct ParserState<ID: 'static> {
   positional_index: usize,
   expects_arg: Option<(&'static str, &'static Opt<ID>)>,
+  required_param_presences: RequiredParamsBitSet,
 }
 
 impl<ID> Default for ParserState<ID> {
   fn default() -> Self {
     Self {
       positional_index: 0,
-      expects_arg: None
+      expects_arg: None,
+      required_param_presences: Default::default(),
     }
   }
 }
@@ -134,13 +140,21 @@ impl<ID: 'static> Opts<ID> {
       return ParseResult::ExitError;
     }
 
-    //TODO: Ensure all required parameter arguments have been provided
-
-    // Ensure that all required positional arguments have been provided
-    for option in self.options[state.positional_index..].iter() {
-      if matches!(option.r#type, OptType::Positional) && option.is_required() {
-        error(program_name, ParseError::RequiredPositional(option.first_name()));
-        return ParseResult::ExitError;
+    // Ensure that all required arguments have been provided
+    let mut required_flag_idx = 0;
+    for (i, option) in self.options.iter().enumerate() {
+      match option.r#type {
+        OptType::Positional => if i >= state.positional_index && option.is_required() {
+          error(program_name, ParseError::RequiredPositional(option.first_name()));
+          return ParseResult::ExitError;
+        }
+        OptType::Flag | OptType::Value => if option.is_required() {
+          if !state.required_param_presences.get(required_flag_idx) {
+            error(program_name, ParseError::RequiredParameter(option.first_name()));
+            return ParseResult::ExitError;
+          }
+          required_flag_idx += 1;
+        }
       }
     }
 
@@ -176,11 +190,26 @@ impl<ID: 'static> Opts<ID> {
         let (option_str, value_str) = token.split_once("=")
           .map_or((token, None), |(k, v)| (k, Some(v)));
 
+        // Keep track of how many required options we've seen
+        let mut required_idx = 0;
+
         // Match a suitable option by name (ignoring the first flag character & skipping positional arguments)
         let (name, option) = self.options.iter()
-          .filter(|opt| matches!(opt.r#type, OptType::Flag | OptType::Value))
-          .find_map(|opt| opt.match_name(option_str, 1).map(|name| (name, opt)))
-          .ok_or(ParseError::UnknownOption(option_str))?;
+          .filter(|opt| matches!(opt.r#type, OptType::Flag | OptType::Value)) .find_map(|opt| {
+            if let Some(name) = opt.match_name(option_str, 1) {
+              Some((name, opt))
+            } else {
+              if opt.is_required() {
+                required_idx += 1
+              }
+              None
+            }
+          }) .ok_or(ParseError::UnknownOption(option_str))?;
+
+        // Mark required option as visited
+        if option.is_required() {
+          state.required_param_presences.insert(required_idx, true);
+        }
 
         match (&option.r#type, value_str) {
           // Call handler for flag-only options
diff --git a/src/lib.rs b/src/lib.rs
index aad691e..42c15a7 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -6,6 +6,7 @@
 #![no_std]
 
 mod const_utf8;
+mod ordered_bitset;
 
 include!("option.rs");
 include!("options.rs");
diff --git a/src/options.rs b/src/options.rs
index d63f64c..960d780 100644
--- a/src/options.rs
+++ b/src/options.rs
@@ -13,9 +13,26 @@ pub struct Opts<ID: 'static> {
   description: Option<&'static str>,
 }
 
+type BitSetType = u32;
+const BITSET_SLOTS: usize = 4;
+/// The maximum amount of allowed required non-positional options.
+pub const MAX_REQUIRED_OPTIONS: usize = BitSetType::BITS as usize * BITSET_SLOTS;
+
 impl<ID: 'static> Opts<ID> {
   /// Build argument parser options with the default flag character of '-'
   pub const fn new(options: &'static[Opt<ID>]) -> Self {
+    // Validate passed options
+    let mut opt_idx = 0;
+    let mut num_required_parameters = 0;
+    while opt_idx < options.len() {
+      if matches!(options[opt_idx].r#type, OptType::Flag | OptType::Value) && options[opt_idx].is_required() {
+        num_required_parameters += 1;
+      }
+      opt_idx += 1;
+    }
+    assert!(num_required_parameters <= MAX_REQUIRED_OPTIONS,
+      "More than 128 non-positional required option entries is not supported at this time");
+
     Self {
       options,
       flag_chars: "-",
diff --git a/src/ordered_bitset.rs b/src/ordered_bitset.rs
new file mode 100644
index 0000000..9784327
--- /dev/null
+++ b/src/ordered_bitset.rs
@@ -0,0 +1,65 @@
+/* jaarg - Argument parser
+ * SPDX-FileCopyrightText: (C) 2025 Gay Pizza Specifications
+ * SPDX-License-Identifier: MIT
+ */
+
+#![allow(private_bounds)]
+
+use core::ops::{BitAnd, BitAndAssign, BitOrAssign, Not, Shl};
+
+pub(crate) struct OrderedBitSet<T: OrderedBitSetStorage, const S: usize>([T; S]);
+
+impl<T: OrderedBitSetStorage, const S: usize> Default for OrderedBitSet<T, S> {
+  fn default() -> Self { Self::new() }
+}
+
+// TODO: Obvious target for improvement when const traits land
+impl<T: OrderedBitSetStorage, const S: usize> OrderedBitSet<T, S> {
+  pub(crate) const fn new() -> Self { Self([T::ZERO; S]) }
+
+  pub(crate) fn insert(&mut self, index: usize, value: bool) {
+    let array_idx = index >> T::SHIFT;
+    debug_assert!(array_idx < S, "Index out of range");
+    let bit_idx = index & T::MASK;
+    let bit_mask = T::from_usize(0b1) << T::from_usize(bit_idx);
+    if value {
+      self.0[array_idx] |= bit_mask;
+    } else {
+      self.0[array_idx] &= !bit_mask;
+    }
+  }
+
+  pub(crate) fn get(&self, index: usize) -> bool {
+    let array_idx = index >> T::SHIFT;
+    debug_assert!(array_idx < S, "Index out of range");
+    let bit_idx = index & T::MASK;
+    let bit_mask = T::from_usize(0b1) << T::from_usize(bit_idx);
+    (self.0[array_idx] & bit_mask) != T::from_usize(0)
+  }
+}
+
+trait OrderedBitSetStorage: Default + Copy + Clone + Eq + PartialEq
+    + BitAnd<Output = Self> + Shl<Output = Self> + Not<Output = Self>
+    + BitAndAssign + BitOrAssign {
+  const ZERO: Self;
+  const SHIFT: u32;
+  const MASK: usize;
+  fn from_usize(value: usize) -> Self;
+}
+
+macro_rules! impl_bitset_storage {
+  ($t:ty, $b:expr) => {
+    impl OrderedBitSetStorage for $t {
+      const ZERO: $t = 0;
+      const SHIFT: u32 = $b.ilog2();
+      const MASK: usize = $b as usize - 1;
+      fn from_usize(value: usize) -> $t { value as $t }
+    }
+  };
+}
+
+impl_bitset_storage!(u8,  u8::BITS);
+impl_bitset_storage!(u16, u16::BITS);
+impl_bitset_storage!(u32, u32::BITS);
+impl_bitset_storage!(u64, u64::BITS);
+impl_bitset_storage!(u128, u128::BITS);