diff --git a/longest_collatz_sequence.rs b/longest_collatz_sequence.rs
new file mode 100644
index 0000000..4d2dfb1
--- /dev/null
+++ b/longest_collatz_sequence.rs
@@ -0,0 +1,33 @@
+fn collatz_sequence(starting_num: u64) -> Vec<u64> {
+    let mut num = starting_num;
+    let mut result: Vec<u64> = vec![];
+
+    result.push(num);
+
+    while num != 1 {
+        if num % 2 == 0 {
+            num /= 2;
+            result.push(num);
+        } else {
+            num = (3*num)+1;
+            result.push(num);
+        }
+    }
+
+    result
+}
+
+fn main() {
+    let mut increment: u64 = 0;
+    let mut longest: u64 = 0;
+
+    for i in 1..=1000000 {
+        let length = collatz_sequence(i).len() as u64;
+        if length > longest {
+            longest = length;
+            increment = i;
+        }
+    }
+
+    println!("{:?}", increment);
+}