Is the image inside a table cell? In that case, you can hide the table border. Select the table. In the Paragraph group, click the arrow on the borders button, and choose Borders and Shading. On the Borders tab, click "None." Click OK.

If you have a picture with a border, right-click the border and choose Format Picture. In the Line Color category, click "No line," and then click Close.

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Stefan Blom
Microsoft Word MVP

Microsoft 365 apps for business
Windows 11 Professional