There are several reputable online courses available to learn data structures. Here are a few highly regarded options:

1. “Algorithms and Data Structures” on Coursera: Offered by the University of California San Diego, this course provides a comprehensive introduction to data structures and algorithms. It covers essential topics such as arrays, linked lists, trees, graphs, and sorting algorithms.

1. “Data Structures and Algorithms” on edX: This course, provided by Microsoft, focuses on fundamental data structures and algorithms commonly used in programming. It covers topics such as arrays, stacks, queues, trees, and sorting algorithms. The course also emphasizes problem-solving techniques.

1. “Data Structures and Algorithms Specialization” on Coursera: This specialization offered by the University of California San Diego consists of a series of courses that cover various data structures and algorithms in detail. It includes courses on graph algorithms, string algorithms, algorithmic toolbox, and more.

1. “Introduction to Data Structures & Algorithms in Java” on Udemy: This course is designed for beginners and provides a solid foundation in data structures and algorithms using the Java programming language. It covers topics such as arrays, linked lists, stacks, queues, trees, and sorting algorithms.

1. “Data Structures and Algorithms: Deep Dive Using Java” on Udemy: This course is suitable for intermediate-level learners and focuses on data structures and algorithms using Java. It covers topics like hash tables, heaps, graphs, dynamic programming, and more.

It’s essential to consider your current programming experience, learning preferences, and the programming language you want to focus on while choosing a course. Additionally, reading reviews, checking the syllabus, and considering the instructor’s expertise can help you make an informed decision.