In how many ways can Alice, Bob, Charlie, David, and Eve split $18$ marbles among themselves so that no two of them have the same number of marbles?
1. **Understanding the problem**: We need to distribute 18 marbles among 5 people (Alice, Bob, Charlie, David, and Eve) such that no two people have the same number of marbles. This means each person must have a unique number of marbles.

2. **Assigning unique numbers**: Since no two people can have the same number of marbles, the possible number of marbles each person can have must be distinct integers. Let's denote the number of marbles each person has as \(a_1, a_2, a_3, a_4, a_5\) where \(a_1 > a_2 > a_3 > a_4 > a_5\).

3. **Sum of unique integers**: The sum of the first 5 distinct positive integers is:
   \[
   0 + 1 + 2 + 3 + 4 = 10
   \]
   Since we need the sum to be 18, we need to find a set of 5 distinct integers that sum to 18.

4. **Finding the correct set**: We can start with the smallest set of distinct integers and adjust them to sum to 18. Let's start with the smallest set:
   \[
   0, 1, 2, 3, 4
   \]
   The sum is 10. To make the sum 18, we need to add 8 more. We can distribute this 8 among the integers while keeping them distinct. One possible way is:
   \[
   0 + 1 + 2 + 3 + 12 = 18
   \]
   However, this set is not valid because 12 is not distinct from the others. We need to find another set.

5. **Correct set of integers**: Let's try:
   \[
   0, 1, 2, 3, 12
   \]
   This set is not valid. Let's try:
   \[
   0, 1, 2, 4, 11
   \]
   This set is not valid. Let's try:
   \[
   0, 1, 3, 4, 10
   \]
   This set is not valid. Let's try:
   \[
   0, 2, 3, 4, 9
   \]
   This set is not valid. Let's try:
   \[
   1, 2, 3, 4, 8
   \]
   This set is valid because:
   \[
   1 + 2 + 3 + 4 + 8 = 18
   \]

6. **Counting permutations**: Now, we need to count the number of ways to assign these numbers to Alice, Bob, Charlie, David, and Eve. There are \(5!\) (5 factorial) ways to permute these 5 numbers:
   \[
   5! = 120
   \]

7. **Conclusion**: Therefore, the number of ways to distribute 18 marbles among 5 people such that no two people have the same number of marbles is:
   \[
   \boxed{120}
   \]