diff --git a/Cargo.lock b/Cargo.lock
index 4f44b51..b307929 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -190,6 +190,13 @@ dependencies = [
  "criterion",
 ]
 
+[[package]]
+name = "day03"
+version = "0.1.0"
+dependencies = [
+ "criterion",
+]
+
 [[package]]
 name = "either"
 version = "1.8.0"
diff --git a/Cargo.toml b/Cargo.toml
index d52cdc3..b5a41d5 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -2,4 +2,5 @@
 members = [
     "day01",
     "day02",
+    "day03",
 ]
diff --git a/day03/Cargo.toml b/day03/Cargo.toml
new file mode 100644
index 0000000..442e67a
--- /dev/null
+++ b/day03/Cargo.toml
@@ -0,0 +1,11 @@
+[package]
+name = "day03"
+version = "0.1.0"
+edition = "2021"
+
+[dev-dependencies]
+criterion = "0.4.0"
+
+[[bench]]
+name = "day03"
+harness = false
\ No newline at end of file
diff --git a/day03/benches/day03.rs b/day03/benches/day03.rs
new file mode 100644
index 0000000..3b48208
--- /dev/null
+++ b/day03/benches/day03.rs
@@ -0,0 +1,27 @@
+use criterion::{black_box, criterion_group, criterion_main, Criterion};
+use ::day03::{parse_input_part1, parse_input_part2, count_valid};
+
+pub fn criterion_benchmark(c: &mut Criterion) {
+    let input = include_str!("../../input/day03.txt");
+    c.bench_function("day03 parse_input_part1", |b| {
+        b.iter(|| parse_input_part1(black_box(input)))
+    });
+    c.bench_function("day03 parse_input_part2", |b| {
+        b.iter(|| parse_input_part2(black_box(input)))
+    });
+    let input_part1 = parse_input_part1(input);
+    c.bench_function("day03 solve_part1", |b| {
+        b.iter(|| count_valid(black_box(&input_part1)))
+    });
+    let input_part2 = parse_input_part2(input);
+    c.bench_function("day03 solve_part2", |b| {
+        b.iter(|| count_valid(black_box(&input_part2)))
+    });
+}
+
+criterion_group!{
+    name = benches;
+    config = Criterion::default().sample_size(1000);
+    targets = criterion_benchmark
+}
+criterion_main!(benches);
diff --git a/day03/src/lib.rs b/day03/src/lib.rs
new file mode 100644
index 0000000..8d51629
--- /dev/null
+++ b/day03/src/lib.rs
@@ -0,0 +1,63 @@
+pub struct Triangle {
+    a: u16,
+    b: u16,
+    c: u16,
+}
+
+impl Triangle {
+    fn new(a: u16, b: u16, c: u16) -> Self {
+        Triangle { a, b, c }
+    }
+    fn is_valid(&self) -> bool {
+        (self.a + self.b > self.c) && (self.a + self.c > self.b) && (self.b + self.c > self.a)
+    }
+}
+
+pub fn parse_input_part1(input: &str) -> Vec<Triangle> {
+    input
+        .lines()
+        .map(|line| {
+            let sides = std::str::from_utf8(line.as_bytes())
+                .unwrap()
+                .split_whitespace()
+                .filter_map(|s| s.parse().ok())
+                .collect::<Vec<u16>>();
+            match sides.as_slice() {
+                [a, b, c] => Triangle::new(*a, *b, *c),
+                _ => panic!("Parse error"),
+            }
+        })
+        .collect()
+}
+
+pub fn parse_input_part2(input: &str) -> Vec<Triangle> {
+    let mut sides = [[0u16; 3]; 3];
+    input
+        .lines()
+        .enumerate()
+        .flat_map(|(i, line)| {
+            let numbers: Vec<u16> = line
+                .split_whitespace()
+                .map(|n| n.parse().unwrap())
+                .collect();
+
+            numbers.iter().enumerate().for_each(|(j, number)| {
+                sides[i % 3][j] = *number;
+            });
+
+            if i % 3 == 2 {
+                let triangles: Vec<Triangle> = (0..3)
+                    .map(|j| Triangle::new(sides[0][j], sides[1][j], sides[2][j]))
+                    .collect();
+
+                return triangles.into_iter();
+            }
+
+            Vec::new().into_iter()
+        })
+        .collect()
+}
+
+pub fn count_valid(triangles: &[Triangle]) -> u16 {
+    triangles.iter().filter(|t| t.is_valid()).count() as u16
+}
diff --git a/day03/src/main.rs b/day03/src/main.rs
new file mode 100644
index 0000000..897fd35
--- /dev/null
+++ b/day03/src/main.rs
@@ -0,0 +1,34 @@
+use ::day03::{parse_input_part1, parse_input_part2, count_valid};
+
+fn main() {
+    let input = include_str!("../../input/day03.txt");
+    let part1_input = parse_input_part1(input);
+    let part1 = count_valid(&part1_input);
+    println!("Part1: {}", part1);
+    let part2_input = parse_input_part2(input);
+    let part2 = count_valid(&part2_input);
+    println!("Part2: {}", part2);
+}
+
+#[cfg(test)]
+mod day03 {
+    use ::day03::{parse_input_part1, parse_input_part2, count_valid};
+
+    const INPUT1: &str = "5 10 25";
+    const INPUT2: &str = r#"101 301 501
+102 302 502
+103 303 503
+201 401 601
+202 402 602
+203 403 603"#;
+
+    #[test]
+    fn part1_test() {
+        assert_eq!(count_valid(&parse_input_part1(INPUT1)), 0);
+    }
+
+    #[test]
+    fn part2_test() {
+        assert_eq!(count_valid(&parse_input_part2(INPUT2)), 6);
+    }
+}