There are numerous online platforms offering Microsoft Excel certification courses. The best course for you depends on your current skill level, the depth of knowledge you're seeking, and your preferred learning style. Here are some reputable online platforms where you can find Microsoft Excel certification courses:

1. Microsoft Learn:

   • Microsoft Certified: Data Analyst Associate: This certification involves skills in Excel for data analysis, among other things.

2. LinkedIn Learning:

   • Microsoft Excel Essential Training: Comprehensive courses suitable for beginners and intermediate users.

3. Udemy:

   • Microsoft Excel - Excel from Beginner to Advanced: This course covers Excel basics to advanced topics.

4. Coursera:

   • Excel Skills for Business Specialization: Offered by Macquarie University, this specialization covers Excel skills for business applications.

5. edX:

   • Data Science and Machine Learning Bootcamp with R and Python: While not exclusively focused on Excel, this Harvard University course includes Excel in the curriculum and covers data analysis using various tools.

6. Skillshare:

   • Microsoft Excel - Excel from Beginner to Advanced: An intermediate-level course covering various Excel features.

7. DataCamp:

   • Intermediate Spreadsheets for Data Science: This course is part of DataCamp's data science track and focuses on using Excel for data analysis.

8. Pluralsight:

   • Excel Fundamentals: This course is suitable for beginners and covers Excel fundamentals.

9. Goskills:

   • Microsoft Excel - Basic & Advanced: Comprehensive courses covering basic to advanced Excel skills.

Before enrolling in a course, consider the content, reviews, and the specific skills covered. Also, check whether the course provides a certification upon completion. Additionally, keep in mind that while online courses can enhance your skills, practical application and hands-on experience are crucial for mastering Excel.