Processing large quantities of data is a common scenario for parallel applications. While distributed memory applications are able to improve the performance of their I/O operations by using parallel I/O libraries, there is no support for parallel I/O operations for applications using shared-memory programming models such as OpenMP available as of today. This paper presents parallel I/O interfaces for OpenMP. We discuss the rationale of our design decisions, present the interface specification, an implementation within the OpenUH compiler and discuss a number of optimizations performed. We demonstrate the benefits of this approach on different file systems for multiple benchmarks and application scenarios. In most cases, we observe significant improvements in I/O performance as compared to the sequential version. Furthermore, we perform a comparison of the OpenMP I/O functions introduced in this paper to message passing interface I/O, and demonstrate the benefits of the new interfaces.